ON L(2, 1)-LABELINGS OF SOME PRODUCTS OF ORIENTED CYCLES

We refine two results of Jiang, Shao and Vesel on the L(2, 1)-labeling number lambda of the Cartesian and the strong product of two oriented cycles. For the Cartesian product, we compute the exact value of lambda((C-m) over right arrow rectangle(C-n) over right arrow) for m, n >= 40; in the case of strong product, we either compute the exact value or establish a gap of size one for lambda((C-m) over right arrow boxed times (C-n) over right arrow) for m, n >= 48.