Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach ty » sach y, sach tu, sach thu
cuu tre » cau tren, cau treo
hang di » hang doi, hang vi, hang dien
va hang » van hang, va nang, va lang
cua tre » cua te, cua triet, dua tren
nang xa » nang x, lang xa, nang ma
ty nang » ky nang, ty xang, ty hang
va cam » va cham, va cac, va cai
va cao » va cac, va co, va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ty nang xa hoi. hieu ((va cam) OR (va cao)) tu va hang di ((cuu tre) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty nang xa hoi. hieu ((va cam) OR (va cao)) tu va hang di ((cuu tre) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ty nang xa hoi. hieu ((va cam) OR (va cao)) tu va hang di ((cuu tre) or (cua tre))".
• Adding a wildcard symbol may retrieve word variants: doc sach ty nang xa hoi. hieu ((va cam) OR (va cao)) tu va hang di ((cuu tre) or (cua tre))*.