WASET
Martinjak, I. , Pavcevic, M.. "BIBD-s for (13, 5, 5), (16, 6, 5) and (21, 6, 4) Possessing Possibly an Automorphism of Order 3". World Academy of Science, Engineering and Technology, Open Science Index 34, International Journal of Mathematical and Computational Sciences (2009), 3(10), 846 - 849.