Complexity of Haemers' minimum rank
Computing min rank is NP-hard:


Rene Peeters, "Orthogonal Representation over Finite Fields and the Chromic Numbr of Graphs", 1996.
Salim Y. El Rouayheb, Mohammad Asad R. Chaudhry, Alex Sprintson, "On the Minimum Number of Transmissions in Single-Hop Wireless Coding Networks", 2007.