FORCED SUPERLINEAR OSCILLATIONS VIA PICONE'S IDENTITY
J. JAROS, T. KUSANO and N. YOSHIDA
Abstract.
In the paper a nonlinear version of an identity known in the literature as the Picone's formula is derived and then it is used to extend the classical Sturmian comparison theory to forced superlinear equations of the second order.
Compressed Postscript 
