Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
van nang » van quang, van ban, van dong
hang di » hang doi, hang vi, hang dien
va hang » van hang, va nang, va lang
cac luc » cau luc, coc luc, cac nuoc
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
v nang » va nang, vu nang, voi nang
luc va » duc va, tuc va, loc va
di cua » dai cua, doi cua, de cua

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