MORGAN, Luke, SPIGA, Pablo and VERRET, Gabriel, 2015, On the order of Borel subgroups of group amalgams and an application to locally-transitive graphs. [online]. 2015. Vol. 434, no. 7, p. 138–152. [Accessed 5 April 2025]. DOI 10.1016/j.jalgebra.2015.02.029. Retrieved from: http://dx.doi.org/10.1016/j.jalgebra.2015.02.029