A remark on graph operators
Bohdan Zelinka · Mathematica Bohemica · 1999
A theorem is proved which implies affirmative answers to the problems of E. Prisner. One problem is whether there are cycles of the line graph operator $L$ with period other than 1, the other whether there are cycles of the 4-edge graph operator $ abla_4$ with period greater than 2. Then a similar theorem follows.