Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, nam thu, nam tu
hanh tai » thanh tai, hang tai, han tai
nang xa » nang x, lang xa, nang ma
va hanh » van hanh, va thanh, va danh
tai cua » thai cua, tai cuc, tri cua
cua te » cua tu

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

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