Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
nang cai » nang cao, nang cap, nang can
nang tai » hang tai, tang tai, sang tai
hieu van » hieu va, thien van, lieu va
van tham » van thanh, van tuan, van chat
vat hanh » vat thanh, van hanh, va hanh
hanh dai » hanh tai, hanh dao, vanh dai
vu sach » su sach, 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: ((vu sach) OR (vu bach)) ky ((nang cai) or (nang tai)) hoi. hieu van tham thuc vat hanh dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (vu bach)) ky ((nang cai) OR (nang tai)) hoi. hieu van tham thuc vat hanh dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) OR (vu bach)) ky ((nang cai) or (nang tai)) hoi. hieu van tham thuc vat hanh dai cua te".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) OR (vu bach)) ky ((nang cai) or (nang tai)) hoi. hieu van tham thuc vat hanh dai cua te*.