Erdős Number

A shortest path from me to Paul Erdős is:
T. Sun → J. L. Gross → F. Harary → P. Erdős
via the papers
Genus distributions of cubic series-parallel graphs
J. L. Gross, M. Kotrbčik, T. Sun, Discrete Math. and Theoretical Comp. Sci. 16(3) (2014)
Some problems in topological graph theory
J. L. Gross, F. Harary, J. Graph Theory 4(3) (1980)
On the dimension of a graph
P. Erdős, F. Harary, W. T. Tutte, Mathematika 12(2) (1965)