Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » thien van, lieu va, hieu ve
van hanh » van thanh, ban hanh, van anh
luoc van » luoc can, luoc va, luc van
cau luoc » cau luc, muu luoc, hau loc
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
y tang » ky tang, 6 tang, 7 tang
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: thu sach y tang ma hoi. ((hieu van) OR (hieu va)) cau luoc van hanh di ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y tang ma hoi. ((hieu van) OR (hieu va)) cau luoc van hanh di ((cua tre) OR (cuu tre))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y tang ma hoi. ((hieu van) OR (hieu va)) cau luoc van hanh di ((cua tre) or (cuu tre))*".