%0 Journal Article %T ACTA MATHEMATICA UNIVERSITATIS COMENIANAE %A J. JAROS %A T. KUSANO and N. YOSHIDA %J ACTA MATHEMATICA UNIVERSITATIS COMENIANAE %D 2000 %I Acta Mathematica Universitatis Comenianae %X . 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. %K . Forced superlinear equation %K Picone's identity %K Sturmian comparison theorems %U http://www.emis.de/journals/AMUC/_vol-69/_no_1/_jaros/jaros.html