Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, ca tren, cau treo
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
danh ve » dinh ve, hanh ve, anh ve
x hoi » o hoi, x ho, 5 hoi

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 ky nang ((x hoi) or (xa hoi)). hieu van nam thuc va danh ve ((cau tren) OR (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x hoi) OR (xa hoi)). hieu van nam thuc va danh ve ((cau tren) OR (dau tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((x hoi) or (xa hoi)). hieu van nam thuc va danh ve ((cau tren) OR (dau tren))*".