Perhaps you should try some spelling variations:
cham duc » pham duc, cham soc, pham duy
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
duc van » duc va, duc tan, duc manh
tai su » tai so, lai su, tai du

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 ((tai su) OR (tai tu)) triet~.
• 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 ((tai su) OR (tai tu)) triet.
• 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 ((tai su) OR (tai tu)) triet".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang ma) or (nang x)) hoi. hieu ve cham duc van hanh ((tai su) OR (tai tu)) triet*.