On determining the location of complex zeros of solutions of certain linear differential equations (Q1113341)

The author investigates the location of zeros of solutions for a class of second-order linear differential equations. In the first part of the paper (Introduction) he makes a presentation of the problem, a survey concerning the results on this problem and shows that it suffices to consider only the following two cases (A) \(m>0\) and \(b<0\), (B) \(0\leq q\leq m\) and \(b>0\). He gives also three theorems concerning the problem in these cases. In the second part of the paper (concepts from the Strodt theory) he proves a lot of lemmas in view to prove the three theorems given in the first part. The key tool in the proofs of Theorems 1, 2 and 3 are asymptotic existence theorems which were proved by W. Strodt.