Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
doi hang » doi khang, voi hang, doi hanh
hang tai » hang va, dung tai
hieu van » hieu va, thien van, lieu va
thuc dan » thuc hanh, hoc dan, thuc vat
dan hanh » dang hanh, dan khanh, dan thanh
cua viet » ca viet, hoa viet, cua dieu
tu sach » thu sach, su sach, te sach
tai hoi » tai khoi, dai hoi, tai hai
van am » van nam, van lam, van dam

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 doi hang tai hoi. hieu van am thuc dan hanh vi ((cua viet) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi hang tai hoi. hieu van am thuc dan hanh vi ((cua viet) OR (cua vat)).
• Adding a wildcard symbol may retrieve word variants: tu sach doi hang tai hoi. hieu van am thuc dan hanh vi ((cua viet) or (cua vat))*.