Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam truc » nam truoc, nam thuc, nam trung
tu cach » tu cac
nang xa » nang x, lang xa, nang ma
truc va » thuc va, thuc vat, trung va
va hang » van hang, va nang, va lang
dau cua » dai cua, cau cua, dan cua
day cua » dai cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu cach) or (toc sach)) ky nang xa hoi. hieu van nam truc va hang ((dau cua) OR (day cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (toc sach)) ky nang xa hoi. hieu van nam truc va hang ((dau cua) OR (day cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu cach) or (toc sach)) ky nang xa hoi. hieu van nam truc va hang ((dau cua) OR (day cua)) te".
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (toc sach)) ky nang xa hoi. hieu van nam truc va hang ((dau cua) OR (day cua)) te*.