operators

We obtain asymptotic formulas with arbitrary order of accuracy for the eigenvalues and eigenfunctions of a nonselfadjoint ordinary differential operator of order n whose coefficients are Lebesgue integrable on [0,1] and the boundary conditions are strongly regular. The orders of asymptotic formulas are independent of smoothness of the coefficients.C1 Dokuz Eylul Univ, Fac Arts & Sci, Dept Math, TR-35160 Izmir, Turkey.Pamukkale Univ, Fac Arts & Sci, Dept Math, TR-20070 Kinikli, Turkey.Dogus Univ, Fac Arts & Sci, Dept Math & Sci, TR-34722 Istanbul, Turkey