Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
truc van » truc va, thuc van, truc ban
va triet » va thiet, va trien, ve triet
van hanh » van thanh, ban hanh, van anh
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
hanh de » hanh ve, hanh kem
cua tre » cuu tre, cua triet, dua tren
nang ma » tang ma, sang ma, nang cao
va cau » van cau, va cac, va dau
ma hoi » mai hoi, xa hoi, ma hoa
cua te » cua tu

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 nang ma hoi. hieu va cau truc van hanh de ((((cua tre) or (va triet))) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ma hoi. hieu va cau truc van hanh de ((((cua tre) OR (va triet))) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ma hoi. hieu va cau truc van hanh de ((((cua tre) or (va triet))) or (cua te))*.