Perhaps you should try some spelling variations:
nam trung » nam trong, tai trung, ba trung
hieu van » hieu va, thien van, lieu va
nam truc » nam truoc, nam thuc, nam thuoc
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, dau tren, ca tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
cuu tre » cua tre, cau treo

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 xa hoi. hieu van ((nam truc) or (nam trung)) van hanh vi ((cuu tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu van ((nam truc) OR (nam trung)) van hanh vi ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. hieu van ((nam truc) or (nam trung)) van hanh vi ((cuu tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu van ((nam truc) or (nam trung)) van hanh vi ((cuu tre) OR (cau tren))*.