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These transactions publish research in computer-based methods of computational collective intelligence (CCI) and their applications in a wide range of fields such as the semantic web, social networks, and multi-agent systems. TCCI strives to cover new methodological, theoretical and practical aspects of CCI understood as the form of intelligence that emerges from the collaboration and competition of many individuals (artificial and/or natural). The application of multiple computational intelligence technologies, such as fuzzy systems, evolutionary computation, neural systems, consensus theory, etc., aims to support human and other collective intelligence and to create new forms of CCI in natural and/or artificial systems. This thirty-first issue presents 12 selected papers from the 3 rd Seminar on Quantitative Methods of Group Decision Making which was held in November 2017 at the WSB University in Wroclaw.

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An equivalent formulation for the Shapley value.- Reflections on two old Condorcet extensions.- Transforming Games with Affinities from Characteristic into Normal Form.- Comparing Game-Theoretic and Maximum Likelihood Approaches for Network Partitioning.- Comparing results of voting by statistical rank tests.- Remarks on Unrounded Degressively Proportional Allocation.- On the Measurement of Control in Corporate Structures.- The Effect of Brexit on the Balance of Power in the European Union Council revisited: a fuzzy multicriteria attempt.- Robustness of the Government and the Parliament, and Legislative Procedures in Europe.- Should the financial decisions be made as group decisions?.- Diffusion of electric vehicles: an agent-based modelling approach.- Decision progress based on IoT for suitable smart cities.

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