Some oscillation criteria for second order nonlinear ordinary differential equations with damping (Q1263718)

The paper reports oscillation criteria for the equation \[ (r(t)x')'+p(t)x'+q(t)f(x)=0, \] \(t\in [0,\infty)\), r,p,q\(\in C[0,\infty)\), \(r(t)>0\). The analogous criteria were earlier obtained at \(f(x)=x\) by \textit{J. Yan} [(I) Proc. Am. Math. Soc. 90, 277-280 (1984; Zbl 0542.34028), and (II) ibid. 98, 276-282 (1986; Zbl 0622.34027)]. The results of the present paper are generalizations of two theorems from (I). The methods of proof are also similar.