HUDEC, R., HUDEC, L., SILLANPAA, A., TAKALO, L.O., KROLL, P. Long-term monitoring of OJ 287: new data. In: BATTRIC, B., ed. Exploring the gamma-ray universe. Proceedings of the 4th Integral workshop. Noordwijk: ESA Publication Division, 2001, s. 295-296. ESA Special Publications., 459.