Convergence of biorthogonal expansion of a vector-function from the class W1 2,m (G) in eigen and associated vector-functions of fourth order differential operator with matrix coefficients

In the paper an ordinary differential operator of fourth order with summable coefficients is considered. Absolute and uniform convergence of biorthogonal expansion of a vector-function from the class W1 2,m (G), G = (0, 1) in eigen and associated vector-functions of this operator is studied, and the rate of uniform convergence of this expansion in G is estimated.