Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
nam thuc » nam thuoc, am thuc, nam thu
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
ca viet » va viet, hoa viet, san viet
hanh va » hang va, hanh vi
co viet » so viet, o viet, hoc viet
hieu le » hieu ve, hieu he, hieu ly
ky dang » ky nang, ky danh
me hoi » le hoi
le nam » ly nam, he nam, le na

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