Hexib - Hexib helps people to learn easier by connecting them to experts and makers of educational content.
EndNote - Accelerate Your Research. Save time, stay organized, collaborate with colleagues and get published with EndNote 20.
Brilliant.org - Brilliant - Understand concepts and build your problem solving skills with thousands of free problems and examples in math, science, and engineering.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Math Doubts - Math Doubts is a scientific mathematics learning places, targets students, teachers and...
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.