@article {Bertola:DifferentialCMP, title = {Differential systems for biorthogonal polynomials appearing in 2-matrix models and the associated Riemann-Hilbert problem}, journal = {Comm. Math. Phys.}, volume = {243}, number = {2}, year = {2003}, pages = {193{\textendash}240}, issn = {0010-3616}, author = {Marco Bertola and B. Eynard and Harnad, J.} } @article {Bertola:DualityCMP, title = {Duality, biorthogonal polynomials and multi-matrix models}, journal = {Comm. Math. Phys.}, volume = {229}, number = {1}, year = {2002}, pages = {73{\textendash}120}, issn = {0010-3616}, author = {Marco Bertola and B. Eynard and Harnad, J.} }