Perhaps you should try some spelling variations:
tham thuc » pham thuc, tam thuc, thai thuc
nham thuc » nhan thuc, nam thuc, nham thu
van hanh » van thanh, ban hanh, van anh
hanh ki » hanh vi, hanh ky, hanh kien
hieu va » lieu va, hieu qua
sach tu » sach thu, sach ty, sach uu
nang ma » tang ma, sang ma, nang cao
cach tu » cach thuc
su viet » so viet
ma hoi » mai hoi, xa hoi, ma hoa
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: tu ((sach tu) or (cach tu)) nang ma hoi. hieu va ((tham thuc) OR (nham thuc)) van hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tu) OR (cach tu)) nang ma hoi. hieu va ((tham thuc) OR (nham thuc)) van hanh ki su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach tu) or (cach tu)) nang ma hoi. hieu va ((tham thuc) OR (nham thuc)) van hanh ki su viet".
• Adding a wildcard symbol may retrieve word variants: tu ((sach tu) or (cach tu)) nang ma hoi. hieu va ((tham thuc) OR (nham thuc)) van hanh ki su viet*.