International Journal of Mathematics and Mathematical Sciences 
Volume 9 (1986), Issue 2, Pages 409-411
doi:10.1155/S0161171286000510

A digraph equation for homomorphic images

Robert D. Girse and Richard A. Gillman

 Department of Mathematics, Idaho State University, Pocatello 83209, Idaho, USA
Received 20 November 1985

Abstract

The definitions of a homomorphism and a contraction of a graph are generalized to digraphs. Solutions are given to the graph equation ϕ(D)¯=θϕ(D¯).