Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
dang van » hoang van, hang va
hieu va » lieu va, hieu qua
hanh ki » hanh vi, hanh ky, hanh kien
va tham » van tham, va cham, va thanh
te sach » toc sach
sach vu » sach va, sach tu, sach uu
dang ma » dang mau, dang mam, dang mat
su viet » so viet
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach vu ((dang ma) or (dang van)) hoi. hieu va tham thuc van hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach vu ((dang ma) OR (dang van)) hoi. hieu va tham thuc van hanh ki su viet.
• Adding a wildcard symbol may retrieve word variants: te sach vu ((dang ma) or (dang van)) hoi. hieu va tham thuc van hanh ki su viet*.