Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
doc sach » hoc sach, toc sach, nuoc sach
hanh van » thanh van, khanh van, hanh san
hieu voi » hieu moi, lieu voi, hieu loi
su triet » su viet, su tien, ve triet
hieu vi » hieu va, hieu ve, hien vi
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
nang ma » tang ma, sang ma, nang cao
hanh va » hang va, hanh vi
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 nang ma hoi. ((hieu vi) OR (hieu voi)) pham thuc va ((hanh van) or (hanh va)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky nang ma hoi. ((hieu vi) OR (hieu voi)) pham thuc va ((hanh van) OR (hanh va)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky nang ma hoi. ((hieu vi) OR (hieu voi)) pham thuc va ((hanh van) or (hanh va)) su triet".
• Adding a wildcard symbol may retrieve word variants: doc sach ky nang ma hoi. ((hieu vi) OR (hieu voi)) pham thuc va ((hanh van) or (hanh va)) su triet*.