Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh van » thanh van, khanh van, hanh san
thuc day » thuc dan, thuc vat
su triet » su viet, su tien, ve triet
hieu vi » hieu voi, hieu va, hieu ve
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
hanh va » hang va, hanh vi
thuc va » thuc vat, thuc dan
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 ty nang ma hoi. hieu vi pham ((thuc va) or (thuc day)) ((hanh van) or (hanh va)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty nang ma hoi. hieu vi pham ((thuc va) OR (thuc day)) ((hanh van) OR (hanh va)) su triet.
• Adding a wildcard symbol may retrieve word variants: doc sach ty nang ma hoi. hieu vi pham ((thuc va) or (thuc day)) ((hanh van) or (hanh va)) su triet*.