Juan Carlos Valenzuela Camino Balbuena Pedro García-Vázquez Xavier Marcote Extremal K<sub>(s, t)</sub>-free bipartite graphs. 139-144 2006 26 Electronic Notes in Discrete Mathematics http://dx.doi.org/10.1016/j.endm.2006.08.011 db/journals/endm/endm26.html#ValenzuelaBGM06