运用虚拟现实技术研究行人移动行为的几个例子：
Arthur W.B., “Inductive Reasoning and Bounded Rationality», The American Economic Review, vol.84, mai 1994, pp.406-411.
Fajen B.R., et Warren W.H., “Behavioral Dynamics of Steering,Obstable Avoidance, and Route Selection”, Journal of Experimental Psychology, vol.29, avril 2003, p.343.
一条街上的两家酒吧的对比研究：
Drury J., Langston P., et al., “Cooperation Versus Competition in a Mass Emergency Evacuation: A New Laboratory Simulation and a New Theoretical Model”, Behavior Research Methods, vol.41, août 2009, pp.957-970.
Saloma C., Perez G.J., Tapang G., Lim M., et Palmes-Saloma C., “Self organized Queuing and Scale-free Behavior in Real Escape Panic”, art. cité.
8.帮一把，还是快逃开？
Helbing D., Farkas I., et Vicsek T., “Simulating Dynamical Features of Escape Panic”, Nature, vol.407, septembre 2000,pp.487-490.
灾难现场目击者报告：
紧急逃生中的模仿现象：
Darley J. M., et Latané B., “Bystander Intervention in Emergencies:Difusion of Responsibility”, Journal of Personality and Social Psychology,vol.8, avril 1968, pp.377.
Zuriguel I., Garcimartín A., et al., “Effect of Obstacle Position in the Flow of Sheep Through a Narrow Door”, Physical Review E, vol.94, septembre 2016.
施展慷慨行为时的脑成像：
Lin P., Wang G.Y., et al., “An Experimental Study of the Impact of an Obstacle on the Escape Eficiency by Using Mice under High Competition”,Physica A : Statistical Mechanics and its Applications, vol.482, septembre 2017, pp.228-242.
Park S.Q., Tobler P.N., et al., “A Neural Link Between Generosity and Happiness”, Nature Communications, vol.8, juillet 2017.
Helbing D., Buzna L., Johansson A., et Werner T., “Self-organized Pedestrian Crowd Dynamics: Experiments, Simulations, and Design Solutions”, Transportation Science, vol. 39, février 2005, pp.1-24.
人类的利他本性：
关于在出入口附近设置立柱的研究：
Tomasello M., Why We Cooperate, Cambridge, The MIT Press, 2009.
Hardin G., “The Tragedy of the Commons”, Science, vol.162, décembre 1968, pp.1243-1248.
说服的技巧：
关于“社会性困境”的开创性论文：
Guéguen N., et Pascual A., “Evocation of Freedom and Compliance: The‘But You Are Free of...’Technique”, Current Research in Social Psychology,vol.5, septembre 2000, pp.264-270.
Garcimartín A., Pastor J.M., Martín- Gómez C., Parisi D., et Zuriguel I.,“Pedestrian Collective Motion in Competitive Room Evacuation”, Scientifc Reports, vol.7, septembre 2017.
Cialdini R.B., Influence, Port Harcourt/Paris, Businessman/Albin Michel, 1987.
西班牙军人参与的集体逃生实验报告尚未公开发表，但同一批研究者发表过另一篇以学生为对象的实验：
紧张压力使人更慷慨：
Mintz A., “Non-adaptive Group Behavior”, The Journal of Abnormal and Social Psychology, vol.46, avril 1951, pp.150-159.
Rand D.G., Greene J.D., et Nowak M.A., “Spontaneous Giving and Calculated Greed”, Nature, vol.489, septembre 2012, pp.427-430.
亚历山大·明茨的实验：
Buchanan, T.W., et Preston, S.D., “Stress Leads to Prosocial Action in Immediate Need Situations”, Frontiers in Behavioral Neuroscience, vol. 8,janvier 2014, pp.1-6.
Gershenson C., et Helbing D., “When Slower Is Faster», Complexity,vol.21, octobre 2015, pp.9-15.
让实验者紧张起来的温和手段：
Helbing D., Farkas I., et Vicsek T., “Simulating Dynamical Features of Escape Panic”, Nature, vol.407, septembre 2000, pp. 487-490.
Kirschbaum C., Pirke K.M., et Hellhammer D.H., “The “Trier Social Stress Test” - a Tool for Investigating Psychobiological Stress Responses in a Laboratory Setting”, Neuropsychobiology, vol.28, 1993, pp.76-81.
关于“欲速则不达”效应：
“9·11”事件及2005年伦敦地铁恐怖袭击后的走访：
Altshuler E., Noda C., et al., “Symmetry Breaking in Escaping Ants”,The American Naturalist, vol.166, décembre 2005, pp.643-649.
Blake S., Galea E., Westeng H., et Dixon A.J., “An Analysis of Human Behaviour During the WTC Disaster of 11 September 2001 Based on Published Survivor Accounts”, Proceedings of the 3rd International Symposium on Human Behaviour in Fire, vol.1, septembre 2004, pp.181-192.
Saloma C., Perez G.J., Tapang G., Lim M., et Palmes-Saloma C.,“Self-organized Queuing and Scale-free Behavior in Real Escape Panic”,Proceedings of the National Academy of Sciences, vol.100, octobre 2003,pp.11947-11952.
Drury J., Cocking C., et Reicher S., “The Nature of Collective Resilience: Survivor Reactions to the 2005 London Bombings”, International Journal of Mass Emergencies and Disasters, vol.27, mars 2009, pp.66-95.
Garcimartín A., Zuriguel I., et al., “Flow and Clogging of a Sheep Herd Passing Through a Bottleneck”, Physical Review E, vol.91, février 2015.
“泰坦尼克号”上的逃生：
用羊、老鼠、蚂蚁研究逃生行为：
Corrado F., Titanic, Lille, Hachette collections, 2003.
Moussaïd M., Hölscher C., et al., “Crowd Behavior During High-stress Evacuations in an Immersive Virtual Environment”, Journal of the Royal Society Interface, vol.13, septembre 2016.
“旁观者效应”的元分析：
我们用虚拟现实技术模拟的恐慌实验：
Fischer P., Kainbacher M., et al., “The Bystander-effect: A Meta analytic Review on Bystander Intervention in Dangerous and Non-dangerous Emergencies”, Psychological Bulletin, vol.137, juillet 2011, pp.517-537.
7.恐慌，在潘多拉星球上
关于利他行为会“传染”的研究：
Pelé M., Sueur C., et al., “Cultural Influence of Social Information Use in Pedestrian Road-crossing Behaviours”, Royal Society Open Science, vol.4,février 2017.
Tsvetkova M., et Macy M.W., “The Social Contagion of Generosity”,PloS ONE, vol.9, février 2014.
行人过马路行为的文化差异：
Fowler J.H., et Christakis N.A., “Cooperative Behavior Cascades in Human Social Networks”, Proceedings of the National Academy of Sciences,vol.107, mars 2010, pp.5334-5338.
Faria J. J., Krause S., et Krause J., “Collective Behavior in Road Crossing Pedestrians: The Role of Social Information”, Behavioral Ecology, vol.21, novembre 2010, pp. 1236-1242.
9.信息流行病
行人过马路行为研究：
在梅连度进行的埃博拉病毒源头调查：
Nilsson D., et Johansson A., “Social Influence During the Initial Phase of a Fire Evacuation: Analysis of Evacuation Experiments in a Cinema Theatre”, Fire Safety Journal, vol. 44, janvier 2009, pp.71-79.
Saéz A.M., Sachse A., et al., “Investigating the Zoonotic Origin of the West African Ebola Epidemic”, EMBO Molecular Medicine, vol.7, décembre 2014, pp.17-24.
电影院逃生实验：
中世纪黑死病传播研究：
Ward A.J., Sumpter D.J., Couzin I.D., Hart P.J., et Krause J., “Quorum Decision-making Facilitates Information Transfer in Fish Shoals”,Proceedings of the National Academy of Sciences, vol.105, mai 2008,pp.6948-6953.
Noble J.V., “Geographic and Temporal Development of Plagues”,Nature, vol.250, août 1974, pp.726-729.
机器鱼“奸细”实验：
人的移动与疾病传播的关系研究：
Dyer J. R., Johansson A., Helbing D., Couzin I.D., et Krause J.,“Leadership, Consensus Decision Making and Collective Behaviour in Humans”, Philosophical Transactions of the Royal Society of London B:Biological Sciences, vol.364, mars 2009, pp.781-789.
Brockmann D., et Helbing D., “The Hidden Geometry of Complex,Network-driven Contagion Phenomena”, Science, vol.342, décembre 2013,pp.1337-1342.
人群中的5%法则：
脸书上的图像传播实验：
Couzin I.D., Krause J., Franks N.R., et Levin S.A., “Effective Leadership and Decision-making in Animal Groups on the Move”, Nature,vol.433, février 2005, pp.513-516.
Cheng J., Adamic L., Dow P.A., Kleinberg J.M., et Leskovec J., “Can Cascades be Predicted?”, Proceedings of the 23rd International Conference on World Wide Web, avril 2014, pp. 925-936.
几条鱼如何带动整个鱼群：
H1N1流感在推特上的信息传播：
Halloy J., Deneubourg J.L., et al., “Social Integration of Robots into Groups of Cockroaches to Control Self-organized Choices”, Science, vol.318,novembre 2007, pp.1155-1158.
Salathé M., et Khandelwal S., “Assessing Vaccination Sentiments with Online Social Media: Implications for Infectious Disease Dynamics and Control”, PLoS Computational Biology, vol.7, octobre 2011.
蟑螂群中的机器蟑螂：
假新闻传播速度研究：
Faria J., Krause J., et al., “A Novel Method for Investigating the Collective Behaviour of Fish: Introducing ‘Robofish’”, Behavioral Ecology and Sociobiology, vol.64, août 2010, pp.1211-1218.
Vosoughi S., Roy D., et Aral S., “The Spread of True and False News Online”, Science, vol.359, mars 2018, pp.1146-1151.
有关鱼群中的机器鱼：
最早关于信息在传播中的歪曲的研究之一：
Selous E., Thought-Transference (or What?) in Birds, Londres,Constable, 1931.
Bartlett F., Remembering: An Experimental and Social Study,Cambridge, Cambridge University Press, 1932.
关于鸟群是否依靠心灵感应协调行动的报告：
我们关于谣言传播的研究：
Pillot M. H., Gautrais J., Gouello J., Michelena P., et Bon R., “Moving Together: Incidental Leaders and Naive Followers”, Behavioural Processes,vol.83, mars 2010, pp. 235-241.
Moussaïd M., Brighton H., et Gaissmaier W., “The Amplification of Risk in Experimental Difusion Chains”, Proceedings of the National Academy of Sciences, vol.112, avril 2015, pp.5631-5636.
羊群的跟从现象实验：
10.人际网络
6.别人去哪儿我去哪儿
米尔格伦的“六度分隔”研究：
https://en.wikipedia.org/wiki/List_of_human_stampedes
Travers J., et Milgram S., “An Experimental Study of the Small-world Problem”, Sociometry, vol.32, décembre 1969, pp.425-443.
20世纪初以来全球群体踩踏事故名单：
对网络进行科学研究的两篇奠基性论文：
Helbing D., Perc M., et al., “Saving Human Lives: What Complexity Science and Information Systems Can Contribute», Journal of Statistical Physics, vol.158, février 2015, pp. 735-781.
Watts D. J., et Strogatz S.H., “Collective Dynamics of ‘Small-world’Networks”, Nature, vol.393, juin 1998, pp.440-443.
关于群众运动的管理：
Barabási A.L., et Albert R., “Emergence of Scaling in Random Networks”, Science, vol.286, octobre 1999, pp.509-512.
Johansson A., Helbing D., al- Abideen H.Z., et Al-Bosta S., “From Crowd Dynamics to Crowd Safety: A Videobased Analysis”, Advances in Complex Systems, vol.11, mai 2008, pp.497-527.
该领域的两本重要参考书：
安德斯开发的监控录像分析技术：
Barabási A.L., Linked, New York, Plume, 2003.
Helbing D., et Mukerji P., “Crowd Disasters as Systemic Failures:Analysis of the Love Parade Disaster”, EPJ Data Science, vol.1, juin 2012, p.7.
Watts D.J., Six Degrees: The Science of a Connected Age, New York,W.W. Norton & Company, 2004.
“爱的大游行”踩踏事件分析：
克里斯塔基斯和富勒的关于“社交传染”的多项研究成果：
Helbing D., Johansson A., et al-Abideen H.Z., “Dynamics of Crowd Disasters: An Empirical Study”, Physical Review E, vol.75, avril 2007.
Christakis N.A., et Fowler J.H., Connected: The Surprising Power of Our social Networks and How They Shape Our Lives, Boston, Little, Brown and Company, 2009.
麦加朝圣监控录像分析：
Christakis N.A., et Fowler J.H., “The Spread of Obesity in a Large Social Network over 32 Years”, New England Journal of Medicine, vol.357,juillet 2007, pp.370-379.
5.人流汹涌
Christakis N.A., et Fowler J.H., “The Collective Dynamics of Smoking in a Large Social Network”, New England Journal of Medicine, vol.358, mai 2008, pp.2249-2258.
Helbing D., Keltsch J., et Molnar P., “Modelling the Evolution of Human Trail Systems”, Nature, vol.388, juillet 1997, pp.47-50.
Fowler J. H., et Christakis N. A., “Dynamic Spread of Happiness in a Large Social Network: Longitudinal Analysis over 20 years in the Framingham Heart Study”, BMJ, vol.337, décembre 2008, p.2338.
关于行人踩出的路径网络：
脸书用户的心理侧写：
Garnier S., Tache F., Combe M., Grimal A., et Theraulaz G., “Alice in Pheromone Land: An Experimental Setup for the Study of Ant-like Robots”,Swarm Intelligence Symposium 2007, avril 2007, pp.37-44.
Kosinski M., Stillwell D., et Graepel T., “Private Traits and Attributes are Predictable from Digital Records of Human Behavior”, Proceedings of the National Academy of Sciences, vol.110, mars 2013, pp.5802-5805.
Bonabeau E., Dorigo M., et Theraulaz G., Swarm Intelligence: From Natural to Artifcial Systems, Oxford, Oxford University Press, 1999.
对影响力渠道的研究：
关于仿生技术的运用详见：
Aral S., et Walker D., “Identifying Influential and Susceptible Members of Social Networks”, Science, vol.337, juin 2012, pp.337-341.
Goss S., Aron S., Deneubourg J.L., et Pasteels J.M., “Self-organized Shortcuts in the Argentine Ant”, Naturwissenschaften, vol.76, décembre 1989, pp.579-581.
脸书与大选期间的政治动员关系研究：
关于蚂蚁抄近道：
Bond R.M., Fowler J.H., et al., “A 61-million-person Experiment in Social Influence and Political Mobilization”, Nature, vol.489, septembre 2012, p.295.
Dallacker M., Social Determinants of Obesity: How Parents Shape the Eating Behavior and Body Weight of Their Children, thèse de doctorat,université libre de Berlin, 2017.
情绪传染的争议性研究：
马克斯·普朗克研究所一名博士生关于我们的饮食行为与社会关系的论文：
Kramer A.D., Guillory J.E., et Hancock J.T., “Experimental Evidence of Massive-scale Emotional Contagion Through Social Networks”, Proceedings of the National Academy of Sciences of the United States of America, vol.111,juin 2014, p.8788.
Utikal V., et Fischbacher U., “Disadvantageous Lies in Inpidual Decisions”, Journal of Economic Behavior & Organization, vol.85, janvier 2013, pp.108-111.
11.千猜万判铸一智
关于修女说谎的实验参阅：
高尔顿切蛋糕法：
Fischbacher U., et Föllmi-Heusi F., “Lies in Disguise: An Experimental Study on Cheating”, Journal of the European Economic Association, vol.11,juin 2013, pp.525-547.
Galton F., “Cutting a Round Cake on Scientific Principles”, Nature,vol.75, décembre 1906, p.173.
关于作弊和撒谎的实验一例：
19世纪思想家们对大众智慧的负面判断：
Milgram S., “Behavioral Study of Obedience”, The Journal of Abnormal and Social Psychology, vol.67, octobre 1963, pp.371-378.
Le Bon G., Psychologie des Foules, Paris, Félix Alcan, 1895.
斯坦利·米尔格伦的服从行为研究：
Mackay C., Extraordinary Popular Delusions and the Madness of Crowds, Londres, Richard Bentley, 1841.
Asch S.E., “Opinions and Social Pressure”, Scientifc American, vol.193,novembre 1955, pp.31-35.
弗朗西斯·高尔顿关于估算牛重量的文章：
所罗门·阿希的“从众心理”实验：
Galton F., “Vox populi”, Nature, vol.75, mars 1907,pp.450-451.
4.欢迎来到心理学世界
畅销书《群体的智慧》：
Moussaïd M., Helbing D., et Theraulaz G., “How Simple Rules Determine Pedestrian Behavior and Crowd Disasters”, Proceedings of the National Academy of Sciences , vol.108, avril 2011, pp. 6884-6888.
Surowiecki J., The Wisdom of the Crowds, New York, Doubleday Books,2004.
我与赫尔宾的“大众的模式化行为”研究论文：
关于医生群体的智慧：
Montaigne M., Tu mourras moins bête, Roubaix, Ankama, 2011.
Kurvers R.H., Wolf M., et al., “Boosting Medical Diagnostics by Pooling Independent Judgments”, Proceedings of the National Academy of Sciences, vol.113, août 2016, pp.8777-8782.
https://tumourrasmoinsbete.blogspot.com/
Kämmer J.E., Hautz W.E., Herzog S.M., Kunina-Habenicht O., et Kurvers R.H., “The Potential of Collective Intelligence in Emergency Medicine: Pooling Medical Students’Independent Decisions Improves Diagnostic Performance”, Medical Decision Making, vol.37, mars 2017,pp.715-724.
玛丽翁·蒙田的插画博客及漫画《星期四，大众观察日》：
关于多样性预测定理：
Lowry O.H., Rosebrough N.J., Farr A.L., et Randall R.J., “Protein Measurement with the Folin Phenol Reagent”, Journal of Biological Chemistry, vol.193, mai 1951, pp.265-275.
Page S.E., The Diference: How the Power of Diversity Creates Better Groups, Firms, Schools, and Societies, Princeton, Princeton University Press,2008.
1900年以来引用次数最多的科学论文：
社交影响力对集体判断的影响：
Van Noorden R., Maher B., et Nuzzo R., “The Top 100 Papers”,Nature, vol.514, octobre 2014, pp.550-553.
Lorenz J., Rauhut H., Schweitzer F., et Helbing D., “How Social Influence Can Undermine the Wisdom of Crowd Efect”, Proceedings of the National Academy of Sciences, vol.108, mai 2011, pp.9020-9025.
对科学文献引用数的研究：
Muchnik L., Aral S., et Taylor S.J., “Social Influence Bias: A Randomized Experiment”, Science, vol.341, août 2013, pp.647-651.
Helbing D., et Molnar P., “Social Force Model for Pedestrian Dynamics”, art. cité.
学生给教师评分制度的负面影响：
德克·赫尔宾的行人粒子模型：
Eiszler C.F., “College Students’Evaluations of Teaching and Grade Inflation”, Research in Higher Education, vol. 43, août 2002, pp.483-501.
Henderson L.F., “The Statistics of Crowd Fluids”, Nature, vol.229,février 1971, pp.381-383.
文化市场中的集体判断：
用水流模型研究人流：
Salganik M.J., Dodds P.S., et Watts D.J., “Experimental Study of Inequality and Unpredictability in an Artificial Cultural Market”, Science,vol.311, février 2006, pp.854-856.
Moussaïd M., Perozo N., Garnier S., Helbing D., et Theraulaz G., “The Walking Behaviour of Pedestrian Social Groups and its Impact on Crowd Dynamics”, PloS ONE, vol.5, avril 2010.
12.朝阳升起时
我们的“行人小团体”研究成果：
路易斯·冯·安的验证码：
Jacobs H., “To Count a Crowd”, Columbia Journalism Review, vol.6,mai 1967, pp.37-40.
Von Ahn L., Maurer B., McMillen C., Abraham D., et Blum M.,“reCAPTCHA: Human-based Character Recognition via Web Security Measures”, Science, vol.321, septembre 2008, pp.1465-1468.
大众示威游行的人工统计法参见：
大众参与美国国家航空航天局研究的例子：
González M.C., Hidalgo C.A., et Barabási A.L., “Understanding Inpidual Human Mobility Patterns”, Nature, vol.453, juin 2008, pp.779-782.
Westphal A.J., Simionovici A.S., et al., “Evidence for Interstellar Origin of Seven Dust Particles Collected by the Stardust Spacecraft”, Science,vol.345, août 2014, pp. 786-791.
关于利用GPS数据跟踪行人的研究：
众包式科研的成果：
Wikelski M., et Tertitski G., “Living Sentinels for Climate Change Efects”, Science, vol.352, mai 2016, pp. 775-776.
Cooper S., Foldit players, et al., “Predicting Protein Structures with a Multiplayer Online Game”, Nature, vol. 466, août 2010, pp.756-760.
马丁·维克尔斯基发起的太空辅助动物研究国际合作项目（ICARUS）介绍：
Khatib F., Baker D., et al., “Crystal Structure of a Monomeric Retroviral Protease Solved by Protein Folding Game Players”, Nature Structural &Molecular Biology, vol.18, septembre 2011, pp.1175-1177.
3.行人·粒子
Sørensen J.J.W., Sherson J.F., et al., “Exploring the Quantum Speed Limit with Computer Games”, Nature, vol.532, avril 2016, pp.210-213.
Helbing D., et Molnar P., “Social Force Model for Pedestrian Dynamics”, Physical Review E, vol.51, mai 1995, pp.4282-4286.
Gowers T., et Nielsen M., “Massively Collaborative Mathematics”,Nature, vol.461, octobre 2009, pp.879-881.
德克·赫尔宾关于行人自组织的论文：
对维基百科编辑质量的研究：
Vicsek T., Czirók A., Ben-Jacob E., Cohen I., et Shochet O., “Novel Type of Phase Transition in a System of Self- driven Particles”, Physical Review Letters, vol.75, août 1995, pp.1226-1229.
Casebourne I., Davies C., Fernandes M., et Norman N., Assessing the Accuracy and Quality of Wikipedia Entries Compared to Popular Online Encyclopaedias: A Comparative Preliminary Study across Disciplines in English, Spanish and Arabic, Brighton, Epic UK, 2012.
从事大众研究的物理学家关注的粒子相变的相关基础文献：
蚂蚁和白蚁巢穴的构造：
Couzin I.D., et Franks N.R., “Self-organized Lane Formation and Optimized Trafic Flow in Army Ants”, Proceedings of the Royal Society of London B: Biological Sciences, vol. 270, janvier 2003, pp.139-146.
Moreira A.A., Ramos V.M., et al., “External and Internal Structure of Atta bisphaerica Forel (Hymenoptera: Formicidae) Nests”, Journal of Applied Entomology, vol. 128, avril 2004, pp.204-211.
Gotwald W.H., Army Ants: The Biology of Social Predation, Ithaca, Cornell University Press, 1995.
Perna A., Theraulaz G., et al., “The Structure of Gallery Networks in the Nests of Termite Cubitermes spp. Revealed by X-ray Tomography”,Naturwissenschaften, vol.95, mai 2008, pp.877-884.
关于行军蚁以及它们的猎食方阵：
群居型昆虫的建筑行为：
Moussaïd M., Theraulaz G., et al., “Trafic Instabilities in Self-organized Pedestrian Crowds”, PLoS Computational Biology, vol. 8, mars 2012.
Grassé P.P., “La théorie de la stigmergie: essai d’interprétation du comportement des termites constructeurs”, Insectes Sociaux, vol.6, 1959,pp.41-81.
关于环形走廊实验：
后记
2.行人、蚂蚁和米粒
关于大众监测仪的灵感来源“地球神经系统”，它是在2012年欧洲的“信息通信未来”（FutureICT）项目框架下提出的：
Helbing D., Molnár P., Farkas I. J., et Bolay K., “Self-organizing Pedestrian Movement”, Environment and Planning B: Planning and Design,vol.28, juin 2001, pp.361-383.
Giannotti F., Helbing D., et al., “A Planetary Nervous System for Social Mining and Collective Awareness”, The European Physical Journal Special Topics, vol. 214, novembre 2012, pp.49-75.
有关行人靠右避让现象的其他资料：
有关步行加速器的设想：
Moussaïd M., Theraulaz G., et al.,“Experimental Study of the Behavioural Mechanisms Underlying Self-Organization in Human Crowds”,Proceedings of the Royal Society of London B: Biological Sciences, vol. 276,mai 2009, pp.2755-2762.
Marti S., “On va bientôt marcher sur le trottoir intelligent”, La Dépêche,mars 2011.
我的第一篇发表物，关于波尔多的走廊实验：
蜜蜂舞蹈的研究：
1.我的入行洗礼
Von Frisch K., The Dance Language and Orientation of Bees,Cambridge, Harvard University Press, 1967.