Perhaps you should try some spelling variations:
sang mai » sang ma, sang tai, lang mai
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
ca viet » va viet, hoa viet, san viet
thuc va » thuc vat, thuc day
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
co viet » so viet, o viet, hoc viet
y sang » _ sang, duy sang
va nam » van nam, ha nam, va nay

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 y sang mai hoi. hieu va nam ((thuc va) OR (thuc dan)) hanh vi ((ca viet) or (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y sang mai hoi. hieu va nam ((thuc va) OR (thuc dan)) hanh vi ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y sang mai hoi. hieu va nam ((thuc va) OR (thuc dan)) hanh vi ((ca viet) or (co viet))".
• Adding a wildcard symbol may retrieve word variants: su sach y sang mai hoi. hieu va nam ((thuc va) OR (thuc dan)) hanh vi ((ca viet) or (co viet))*.