Perhaps you should try some spelling variations:
cua triet » su triet, va triet
pham thuc » phap thuc, pham chuc, nham thuc
doc sach » hoc sach, toc sach, nuoc sach
hanh tai » thanh tai, hang tai, han tai
cua viet » ca viet, hoa viet, cua vat
hieu vi » hieu voi, hieu va, hien vi
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky sang ma hoi. ((hieu vi) OR (hieu ve)) pham thuc va hanh tai ((cua triet) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky sang ma hoi. ((hieu vi) OR (hieu ve)) pham thuc va hanh tai ((cua triet) OR (cua viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky sang ma hoi. ((hieu vi) OR (hieu ve)) pham thuc va hanh tai ((cua triet) or (cua viet))".
• Adding a wildcard symbol may retrieve word variants: doc sach ky sang ma hoi. ((hieu vi) OR (hieu ve)) pham thuc va hanh tai ((cua triet) or (cua viet))*.