Perhaps you should try some spelling variations:
hieu suat » hieu luat, hieu qua
va triet » va thiet, va trien, ve triet
cua viet » ca viet, hoa viet, cua vat
tang mai » tang ma, tang tai, lang mai
cham duc » pham duc, cham soc, pham duy
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
mai hoi » mai khoi, dai hoi, lai hoi
ty tang » tay tang, ty xang, ty hang
tieu su » thieu so

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ty tang mai hoi. ((hieu suat) or (tieu su)) cham duc va hanh va ((cua viet) or (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty tang mai hoi. ((hieu suat) OR (tieu su)) cham duc va hanh va ((cua viet) OR (va triet)).
• Adding a wildcard symbol may retrieve word variants: tu sach ty tang mai hoi. ((hieu suat) or (tieu su)) cham duc va hanh va ((cua viet) or (va triet))*.