Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
va triet » va thiet, va trien, ve triet
sach thi » sach thu, sach tai, sach thieu
thi hang » thi hanh, thi nang, thi hong
thai va » thai van
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
va tham » van tham, va cham, va thanh
va han » va phan, van han, va hang
ca hoi » cau hoi, cua hoi, co hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach thi hang ((ca hoi) or (xa hoi)). hieu va tham thuc ((va han) OR (va hanh)) thai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thi hang ((ca hoi) OR (xa hoi)). hieu va tham thuc ((va han) OR (va hanh)) thai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thi hang ((ca hoi) or (xa hoi)). hieu va tham thuc ((va han) OR (va hanh)) thai va triet".
• Adding a wildcard symbol may retrieve word variants: tu sach thi hang ((ca hoi) or (xa hoi)). hieu va tham thuc ((va han) OR (va hanh)) thai va triet*.