Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
tham thuc » nham thuc, tam thuc, thai thuc
vanh dai » van dai, vanh tai, lanh dao
nang cau » nang cao, hang cau, nang dau
su sach » so sach
va vanh » va van, va danh, va hanh
hieu ve » hieu va, hieu van
cau hoa » cau hoi
vu sach » vu bach, vu khach
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) OR (vu sach)) ky nang cau hoa. hieu ve ((tham thuc) or (pham thuc)) va vanh dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) ky nang cau hoa. hieu ve ((tham thuc) OR (pham thuc)) va vanh dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (vu sach)) ky nang cau hoa. hieu ve ((tham thuc) or (pham thuc)) va vanh dai cua te".
• Adding a wildcard symbol may retrieve word variants: ((su sach) OR (vu sach)) ky nang cau hoa. hieu ve ((tham thuc) or (pham thuc)) va vanh dai cua te*.