Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
doc sach » hoc sach, toc sach, nuoc sach
va thanh » gia thanh, ban thanh, va tinh
va triet » va thiet, va trien, ve triet
hieu vi » hieu voi, hieu ve, hien vi
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va danh, ban hanh
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
ma hoi » mai hoi, xa hoi, ma hoa
tai va » thai va, mai va, tri va

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