Perhaps you should try some spelling variations:
sach hoi » sach doi, sach moi, cach thoi
hoi nang » hoi lang, ho nang, hoa nang
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
thuc va » thuc vat, thuc dan, thuc day
hanh di » hanh vi, hang di, danh di
hanh de » hanh ve, hanh kem
x hoi » xa hoi, o hoi, x ho

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 hoi nang x hoi. hieu van nam thuc va ((hanh di) or (hanh de)) cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoi nang x hoi. hieu van nam thuc va ((hanh di) OR (hanh de)) cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach hoi nang x hoi. hieu van nam thuc va ((hanh di) or (hanh de)) cua viet*.