University of Isfahan International Journal of Group Theory 2251-7650 3 1 2014 03 01 Co-prolongations of a group extension 57 64 3225 10.22108/ijgt.2014.3225 EN Nguyen Tien Quang Hanoi National University of Education Doan Trong Tuyen National Economics University Nguyen Thi Thu Thuy Hanoi University of Science and Technology Journal Article 2013 02 25 The aim of this paper is to study co-prolongations‎ ‎of central extensions‎. ‎We construct the obstruction theory for‎ ‎co-prolongations‎ ‎and classify the equivalence classes of these by kernels of homomorphisms‎ ‎between 2-dimensional cohomology groups of groups‎. group extension cohomology of groups prolongation obstruction https://ijgt.ui.ac.ir/article_3225_cf176c576d10ffbb3a9c575f460e02e0.pdf