Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
su triet » su viet, su tien, ve triet
cham loc » cham soc, chon loc, cham o
cua viet » ca viet, hoa viet, cua vat
va danh » va dinh, va dan, va hanh
hieu ve » hieu va, hieu van
danh tu » anh tu, doanh thu
ve cham » va cham, ve chat, vu cham
y tang » ky tang, 6 tang, 7 tang
ma hoi » mai hoi, ma hoa, me hoi
loc va » hoc va, luc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach y tang ((ma hoi) OR (xa hoi)). hieu ve cham loc va danh tu ((su triet) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y tang ((ma hoi) OR (xa hoi)). hieu ve cham loc va danh tu ((su triet) OR (cua viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y tang ((ma hoi) OR (xa hoi)). hieu ve cham loc va danh tu ((su triet) or (cua viet))".
• Adding a wildcard symbol may retrieve word variants: toc sach y tang ((ma hoi) OR (xa hoi)). hieu ve cham loc va danh tu ((su triet) or (cua viet))*.