Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
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
ly nang » ky nang, ly vang, ly quang
ly hang » ly quang
cao hoi » cau hoi, co hoi, cao hoc

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 ((ly nang) OR (ly hang)) cao hoi. hieu van nam thuc dan hanh vi ((cua viet) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ly nang) OR (ly hang)) cao hoi. hieu van nam thuc dan hanh vi ((cua viet) OR (cua vat)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ly nang) OR (ly hang)) cao hoi. hieu van nam thuc dan hanh vi ((cua viet) or (cua vat))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ly nang) OR (ly hang)) cao hoi. hieu van nam thuc dan hanh vi ((cua viet) or (cua vat))*.