Linear Methods of Applied Mathematics  
This free text concentrates on mathematical concepts rather than on details of calculations, which are often done with software, such as Maple or Mathematica. It is not necessary to have experience with Maple or Mathematica in order to read this text, nor is it the goal of this text to teach software, but there are links in the text to Maple worksheets and Mathematica notebooks, which perform calculations and provide some supplementary instructive material. 
Mathematical Constants  
This free book is helpful both to readers seeking information about a specific constant, and to readers who desire a panoramic view of all constants coming from a particular field, for example, combinatorial enumeration or geometric optimization. Unsolved problems appear virtually everywhere as well. This work represents an outstanding scholarly attempt to bring together all significant mathematical constants in one place. 
Graph Decompositions: a study in infinite graph theory  
This book is a research monograph offering a comprehensive treatment of the theory of simplicial decompositions of graphs. 
Vector Bundles & KTheory  
The plan is for this to be a fairly short book focusing on topological Ktheory and containing also the necessary background material on vector bundles and characteristic classes. 
Spectral Sequences in Algebraic Topology  
This is intended to be a readable introduction to spectral sequences, with emphasis on their applications to algebraic topology. 
