PageHeader : Funkcialaj Ekvacioj, 19 (1976) 113-132 Title : Some Classical and Nonclassical Singular Title : Perturbation Problems AuthorInfo : By AuthorInfo : F. A. HOWES* AuthorInfo : (University of Wisconsin, U.S.A.) section : 1. Introduction. section : 2. First-order problems. section : 3. Second-order problems. section : 4. Discussion of results. section : 5. Further results on second-order problems. subsection : 6. Some estimates on derivatives. section : References