Convergence in \(L^ 2\) of solutions of equations with a small matrix as coefficient at the derivative (Q750722)

In a series of papers [ibid. 36, No.1, 73-78 (1984; Zbl 0548.34058); Sib. Mat. Zh. 25, No.6, 153-157 (1984; Zbl 0608.34013); Differ. Equations 21, 1154-1158 (1985); translation from Differ. Uravn. 21, No.10, 1717-1723 (1985; Zbl 0616.34046)] the author considered systems with a small matrix at the derivative. The convergence of solutions in \(L^ 2\) was investigated under the assumption that the solution of the degenerate equation was bounded. In this paper the matrix at the derivative is supposed to be small in the \(L^ 4\) norm but is permitted to be unbounded.