Comparison Theorems for Second Order Nonselfadjoint Differential Systems
E. C. Tomastik · SIAM Journal on Mathematical Analysis · 1983
Comparison theorems for conjugate and focal points of $(rx')' + px = 0$ are given where $r(t)$ and $p(t)$ are continuous $n \times n$ matrices. No sign restrictions are made on the elements of r and p, but certain restrictions are made on the comparing equation. All results are new even in the selfadjoint case.