Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cua tren » dua tren, ca tren, cua tre
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 hanh » van hanh, va thanh, va danh
hanh ve » hanh vi, hanh va, hanh kem
ve cua » le cua, de cua, te cua
x hoi » x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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