Logic Portal: http://en.wikipedia.org/wiki/Portal:Logic
Mathematics Portal: http://en.wikipedia.org/wiki/Portal:Mathematics
Physics Portal: http://en.wikipedia.org/wiki/Portal:Physics
Wikiversity: http://en.wikiversity.org/wiki/Main_Page
Logic Portal: http://en.wikipedia.org/wiki/Portal:Logic
Mathematics Portal: http://en.wikipedia.org/wiki/Portal:Mathematics
Physics Portal: http://en.wikipedia.org/wiki/Portal:Physics
Wikiversity: http://en.wikiversity.org/wiki/Main_Page