Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
ban thanh » ban hang
so triet » su triet, so thiet, bo triet
ban hanh » ban hang
vu sach » vu bach, su sach, vu khach
hieu ve » hieu va, hieu van
ve tham » va tham, ve cham, vi tham
y nang » ky nang, ly nang, may nang
v nang » va nang, vu nang, van nang
hai so » dai so, tai so, thai son

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ((y nang) or (v nang)) xa hoi. hieu ve tham thuc ((ban thanh) OR (ban hanh)) hai so triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ((y nang) OR (v nang)) xa hoi. hieu ve tham thuc ((ban thanh) OR (ban hanh)) hai so triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ((y nang) or (v nang)) xa hoi. hieu ve tham thuc ((ban thanh) OR (ban hanh)) hai so triet".
• Adding a wildcard symbol may retrieve word variants: vu sach ((y nang) or (v nang)) xa hoi. hieu ve tham thuc ((ban thanh) OR (ban hanh)) hai so triet*.