Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
va nang » van nang, da nang, cam nang
va hang » van hang, va lang, va hanh
tu sach » thu sach, te sach, tu cach
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
su sach » so sach, vu sach
van cam » van nam, van lam, van cau
ma hoi » mai hoi, xa hoi, ma hoa
de cua » le cua, te cua, dieu cua

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) or (su sach)) ky tang ma hoi. hieu van cam thuc ((va hang) OR (va nang)) de cua triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky tang ma hoi. hieu van cam thuc ((va hang) OR (va nang)) de cua triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky tang ma hoi. hieu van cam thuc ((va hang) OR (va nang)) de cua triet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky tang ma hoi. hieu van cam thuc ((va hang) OR (va nang)) de cua triet*.