Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
dan dai » dat dai, can dai, dan dat
ma hoi » mai hoi, ma hoa, me hoi
va dan » ca dan, va dao, va dau
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 ky nang ((ma hoi) or (xa hoi)). hieu van cau duc va dan dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ((ma hoi) OR (xa hoi)). hieu van cau duc va dan dai cua te*.