2nd hand textbook and assessment book

These websites offer many 2nd hand textbooks and assessment books.

https://carousell.com/

http://bookfishing.com.sg

http://www.secondhandbooks.com.sg/about.php

http://bookinbookout.com/index.html

http://www.usedbook.sg/ad-category/textbooks

I bought 2 books selling at $5 each, which is selling in Popular at $50 each. The books are still in good condition.

You can sell your materials at the same websites too.