Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
pham duy » pham duc
sach ty » sach tu, sach thu, xach tay
lam cua » nam cua, lam chat
va hanh » va thanh, va danh, ban hanh
va pham » van pham, va phat, va phap
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
cua tre » cua te, cuu tre, cua triet
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 ty) OR (sach y)) tang ma hoi. hieu va pham duy ((va hanh) or (van hanh)) lam cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach y)) tang ma hoi. hieu va pham duy ((va hanh) OR (van hanh)) lam cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach y)) tang ma hoi. hieu va pham duy ((va hanh) or (van hanh)) lam cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach y)) tang ma hoi. hieu va pham duy ((va hanh) or (van hanh)) lam cua tre*.