Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
duc manh » suc manh, duc anh, duc minh
tang van » dang van, hoang van, trong van
sach dao » lanh dao
cao anh » cao dang, cao tang, cao bang
su sach » so sach, vu sach
va tham » van tham, va cham, va thanh
nang ma » tang ma, sang ma, nang cao
cua su » qua su

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 dao ((nang ma) or (tang van)) hoi. lieu va tham thuc ((cao anh) or (duc manh)) dai cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach dao ((nang ma) OR (tang van)) hoi. lieu va tham thuc ((cao anh) OR (duc manh)) dai cua su.
• Adding a wildcard symbol may retrieve word variants: su sach dao ((nang ma) or (tang van)) hoi. lieu va tham thuc ((cao anh) or (duc manh)) dai cua su*.