Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
vat hanh » vat thanh, van hanh, va hanh
cau tren » cu tren, dau tren, ca tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hanh ve » hanh vi, hanh va, hanh kem
ve cau » ke cau, va cau, ve cac
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 vat hanh ve cau 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 vat hanh ve cau 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 vat hanh ve cau tren*.