Nikolaos S. Papageorgiou & Vicenţiu D. Rădulescu 
Nonlinear Analysis – Theory and Methods [PDF ebook] 

Preface.- 1.Sobolev Spaces.- 2.Compact Operators and Operators of Monotone Type.-  3.Degree Theories.- 4.Partial Order, Fixed Point Theory, Variational Pronciples.- 5.Critical Point Theory.- 6.Morse Theory and Critical Groups.- References.- Index.

Nikolaos S. Papageorgiou graduated from the Massachusetts Institute of Technology and received his Ph D in Applied Mathematics from Harvard University. He is Professor at the National Technical University of Athens, Greece. He has written more than 800 research papers and ten books.
Vicenţiu  Rǎdulescu received his Ph D and Habilitation from the University of Paris 6 under the supervision of Haim Brezis. He is Senior Researcher at the Institute of Mathematics, Physics and Mechanics in Ljubljana, Professor at the AGH University of Science and Technology in Krakow, and Professorial Fellow at the Institute of Mathematics of the Romanian Academy. He has written more than 300 research papers and ten books.
Dušan Repovš received his Ph D from Florida State University. He is Professor at the University of Ljubljana and Head of the Nonlinear Analysis, Topology, and Geometry Group at the Institute of Mathematics, Physics and Mechanics in Ljubljana. He is the author of more than 400 research papers and 3 books (Kluwer, CRC Press, European Mathematical Society). He is a member of the European Academy of Arts and Sciences.