The Book of Proof by Richard Hammack
This book is an introduction to the standard methods of proving mathematical theorems. It has been approved by the American Institute of Mathematics' Open Textbook Initiative.
The Euler Archive
The Euler Archive is an online resource for Leonhard Euler's original works and modern Euler scholarship. This dynamic library and database provides summaries of and access to digitized versions of original publications, and references to available translations and current research.
The Archive is centered around individual web pages corresponding to (and containing information about) each work written by Leonhard Euler (more than 850 of them!). Most pages also contain copies of the original publications of these works. You can access these pages by using the navigation links on the left sidebar. In addition, the Archive contains historical information concerning the life and times of Leonhard Euler, as well as a significant percentage of Euler's correspondence.
The Euler Archive was created by Dominic Klyve (Central Washington University) and Lee Stemkoski (Adelphi University). Its current Director is Erik Tou (University of Washington, Tacoma). The site has been hosted by the Mathematical Association of America since 2011.
HAL Open Science
HAL is a multidisciplinary open archive that allows research results to be shared in open access, whether published or not. It is at the service of researchers affiliated with academic institutions, whether public or private. In France, HAL is the national archive chosen by the French scientific and academic community for the open dissemination of its research results. The archive is also accessible to researchers affiliated with foreign academic institutions, whether public or private.
Mathematics Matters
Case studies at the UK's Institute of Mathematics & its Applications, showing how modern math research affects people's lives.
