On L_w^2 -quasi-derivatives for solutions of perturbed general quasi-differential equations

This paper is concerned with square integrable quasi-derivatives for any solution of a general quasi-differential equation of nth order with complex coefficients M[y] – wy = wf(t, y^[0],... , y^[n–1]), t [a, b) provided that all rth quasi-derivatives of solutions of M[y] – wy = 0 and all solutions of its normal adjoint are in and under suitable conditions on the function f.