Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
cham duc » pham duc, cham soc, pham duy
van hanh » ban hanh, van anh, van ban
tu sach » thu sach, su sach, te sach
ve cham » va cham, ve chat, vu cham
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
su viet » so viet
tai su » tai so, tai tu, lai 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 y ((nang ma) or (nang x)) hoi. hieu ve cham duc ((van hanh) OR (van thanh)) tai su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang ma) OR (nang x)) hoi. hieu ve cham duc ((van hanh) OR (van thanh)) tai su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang ma) or (nang x)) hoi. hieu ve cham duc ((van hanh) OR (van thanh)) tai su viet".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang ma) or (nang x)) hoi. hieu ve cham duc ((van hanh) OR (van thanh)) tai su viet*.