[1] M. Behzad, G. Chartrand and L. Lesniak-Forster:
Graphs & Digraphs. Prindle, Weber & Schmidt, Boston, 1979.
MR 0525578
[4] L. Nebeský:
A characterization of the set of all shortest path in a connected graph. Math. Boh. 119 (1994), 15–20.
MR 1303548