Johann Hagauer Wilfried Imrich Sandi Klavzar Recognizing Median Graphs in Subquadratic Time. 123-136 1999 215 Theor. Comput. Sci. 1-2 db/journals/tcs/tcs215.html#HagauerIK99 http://dx.doi.org/10.1016/S0304-3975(97)00136-9