[1] B. D. ACHARYA M. N. VARTAK:
On the construction of grapha with given constant valence-difference $(S)$ on each of their lines. Wiss. Z. TH Ilmenau 23 (1977), No 6, 33-60.
MR 0480187
[2] M. BEHZAD G. CHARTRAND:
Introduction to the theory of graphs. Allyn and Bacon, Boston 1971.
MR 0432461
[3] B. GRÜNBAUM:
Convex Polytopes. Wiley and Sons, 1967.
MR 0226496