Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
phau hoc » phap hoc, thai hoc, nha hoc
cua tre » cua te, cua triet, dua tren
hanh ve » hanh vi, hanh va, hanh kem
hanh le » thanh le, hanh de, manh le
sach ky » sac ky, sach y, sach ty
va phau » va phat, va phap, va phan
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
cuu tre » cau tren, cau treo
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: toc sach ky tang ma hoi. hieu va phau hoc va ((hanh le) or (hanh ve)) ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky tang ma hoi. hieu va phau hoc va ((hanh le) OR (hanh ve)) ((cua tre) OR (cuu tre))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky tang ma hoi. hieu va phau hoc va ((hanh le) or (hanh ve)) ((cua tre) OR (cuu tre))*".