Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
cau tren » cu tren, dau tren, ca tren
cham tuc » nham thuc, pham thuc, cham soc
hieu ve » hieu va, hieu van
tu sach » thu sach, te sach, tu cach
cao hoi » cau hoi, co hoi, cao hoc
su sach » so sach, vu sach
va dan » ca dan, va dao, va dau
ca cau » cua cau, cac cau, can cau

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) or (su sach)) ky nang cao hoi. hieu ve ((cham tuc) OR (tham thuc)) va dan ca cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang cao hoi. hieu ve ((cham tuc) OR (tham thuc)) va dan ca cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky nang cao hoi. hieu ve ((cham tuc) OR (tham thuc)) va dan ca cau tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky nang cao hoi. hieu ve ((cham tuc) OR (tham thuc)) va dan ca cau tren*.