Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hanh lam » thanh lap, hanh kem, hanh va
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
vu pham » su pham, vi pham, vu kham
cua tre » cua te, cua triet, dua tren
duc van » duc va, duc tan, duc manh
hieu vu » hieu va, hieu ve, hieu su
tang ma » mang may, tang van
ty tang » tay tang, ty xang, ty hang
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: ((su sach) or (hoc sach)) ty tang ma hoi. hieu vu pham duc van hanh lam ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (hoc sach)) ty tang ma hoi. hieu vu pham duc van hanh lam ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (hoc sach)) ty tang ma hoi. hieu vu pham duc van hanh lam ((cua tre) or (cuu tre))*.