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 ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
ve cam » ve cham, ve cac, va cam
xuc va » duc va, tuc va, luc va
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
thiet » thieu

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) or (nang cao)) hoi. hieu ve cam xuc va dan vi ((cua tre) or (va thiet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((nang xa) OR (nang cao)) hoi. hieu ve cam xuc va dan vi ((cua tre) OR (va thiet)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((nang xa) or (nang cao)) hoi. hieu ve cam xuc va dan vi ((cua tre) or (va thiet))*.