1.The modern approaches INCLUDE sociological approach, economic approach, psychological approach, quantitative approach, simulation approach, system approach, behavioural approach, Marxian approach etc.1.There are three historical roots of group theory: the theory of ALGEBRAIC equations, number theory and geometry. Joseph Louis Lagrange, Niels Henrik Abel and Évariste Galois were early researchers in the field of group theory.2.Systems philosophy is a discipline aimed at constructing a new philosophy (in the sense of worldview) by using systems concepts. The discipline was first described by Ervin Laszlo in his 1972 book INTRODUCTION to Systems Philosophy: Toward a New Paradigm of Contemporary Thought.3.Game theory offers a rigorous set of concepts, relationships, and models that invite myriad applications to problems of political economy. Indeed, game theory can serve as a fundamental modeling technique that can bridge microfoundations of political and economic exchanges, with developmental processes and [...]4.The workshop on ‘Behavioural Approaches in International Law’ is the first event of the newly launched ESIL IG on Social Sciences and International Law. The workshop will be held online on 22-23 APRIL 2021.Until recently, international legal scholarship has largely been premised on the assumption of rational action on the part of key actors in international law, whether those actors be states, international organizations, judges, arbitrators, or government officials. However, recent literature in cognate disciplines, such as international relations and political science, integrates insights from behavioural economics and cognitive psychology in order to construct more descriptively accurate models of decision-making, including those decisions that pertain to international law.