Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
va hang » van hang, va lang, va hanh
va nang » van nang, da nang, cam nang
cua tu » cua tuc, cua su, cua cu

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 ky nang xa hoi. hieu va cac tuc ((va hang) OR (va nang)) tai ((cua te) or (cua tu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang xa hoi. hieu va cac tuc ((va hang) OR (va nang)) tai ((cua te) OR (cua tu)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang xa hoi. hieu va cac tuc ((va hang) OR (va nang)) tai ((cua te) or (cua tu))".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang xa hoi. hieu va cac tuc ((va hang) OR (va nang)) tai ((cua te) or (cua tu))*.