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