Perhaps you should try some spelling variations:
tang mai » tang ma, tang tai, lang mai
van hanh » van thanh, van anh, van ban
ban hanh » ban hang
hoc viet » hoc hien
ky tang » ky nang, ky dang, kho tang
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu va, hieu van
cac tuc » cac toc, cac tu, cac tac
su xac » pu xac, su cac
xac ky » cac ky, sac ky, bac ky
ve cac » va cac, vien cac
vi hoc » li hoc, va hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: su xac ky tang mai hoi. hieu ve cac tuc ((van hanh) or (ban hanh)) vi hoc viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su xac ky tang mai hoi. hieu ve cac tuc ((van hanh) OR (ban hanh)) vi hoc viet.
• Adding a wildcard symbol may retrieve word variants: su xac ky tang mai hoi. hieu ve cac tuc ((van hanh) or (ban hanh)) vi hoc viet*.