@article{10_4153_CJM_1969_165_5,
     author = {Hedrl{\'\i}n, Z. and Mendelsohn, E.},
     title = {The {Category} of {Graphs} with a {Given} {Subgraph-with} {Applications} to {Topology} and {Algebra}},
     journal = {Canadian journal of mathematics},
     pages = {1506--1517},
     year = {1969},
     volume = {21},
     number = {1},
     doi = {10.4153/CJM-1969-165-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1969-165-5/}
}