Dennis P. Geller. Walkwise and admissible mappings between digraphs. Discrete Mathematics, 9(4):375-390, 1974. [doi]
@article{Geller74,
title = {Walkwise and admissible mappings between digraphs},
author = {Dennis P. Geller},
year = {1974},
doi = {10.1016/0012-365X(74)90084-3},
url = {http://dx.doi.org/10.1016/0012-365X(74)90084-3},
researchr = {https://researchr.org/publication/Geller74},
cites = {0},
citedby = {0},
journal = {Discrete Mathematics},
volume = {9},
number = {4},
pages = {375-390},
}