Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
thu sach » tu sach, thuat sach, thuoc sach
sach hoc » cach hoc, sach hoi, mach hoc
cuu cong » cua cong, thu cong, cac cong
khoa hoc » hoa hoc
cong so » cong san, cong hoa
so toan » so tan, so than, bao toan
xua hai » qua hai, cua hai, xuan thai
xa hai » xa thai, xa hoi, xa dai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach hoc tap, nghien cuu cong so toan khoa hoc ((xa hai) or (xua hai)) van thanh san~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach hoc tap, nghien cuu cong so toan khoa hoc ((xa hai) OR (xua hai)) van thanh san.
• Adding a wildcard symbol may retrieve word variants: thu sach hoc tap, nghien cuu cong so toan khoa hoc ((xa hai) or (xua hai)) van thanh san*.