Ira M. Gessel, Walter Shur. Even and Odd Pairs of Lattice Paths with Multiple Intersections. Journal of Combinatorial Theory, Series A, 75(2):243-253, 1996. [doi]
@article{GesselS96,
title = {Even and Odd Pairs of Lattice Paths with Multiple Intersections},
author = {Ira M. Gessel and Walter Shur},
year = {1996},
doi = {10.1006/jcta.1996.0075},
url = {http://dx.doi.org/10.1006/jcta.1996.0075},
researchr = {https://researchr.org/publication/GesselS96},
cites = {0},
citedby = {0},
journal = {Journal of Combinatorial Theory, Series A},
volume = {75},
number = {2},
pages = {243-253},
}