In mathematical models of some physical phenomena a new class of nonlinear Volterra equations appears ([5],[6]). The equations belonging to this class have u = 0 as a solution (trivial solution), but with respect to their physical meaning, nonnegative nontrivial solutions are of prime importance.
@article{urn:eudml:doc:39946, title = {Boyd index and nonlinear Volterra equations.}, journal = {Extracta Mathematicae}, volume = {6}, year = {1991}, pages = {170-172}, mrnumber = {MR1185370}, language = {en}, url = {http://dml.mathdoc.fr/item/urn:eudml:doc:39946} }
Fernández Castillo, Jesús M.; Okrasinski, W. Boyd index and nonlinear Volterra equations.. Extracta Mathematicae, Tome 6 (1991) pp. 170-172. http://gdmltest.u-ga.fr/item/urn:eudml:doc:39946/