Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van nang » van quang, van ban, van dong
qua cac » cua cac
v nang » va nang, vu nang, voi nang
ma hoi » mai hoi, xa hoi, ma hoa
luc va » tuc va, loc va
dau di » da di, dau da, dau do
di cua » dai cua, doi cua, de cua
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 ((v nang) OR (van nang)) ma hoi. hieu qua cac ((luc va) or (duc va)) dau di cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((v nang) OR (van nang)) ma hoi. hieu qua cac ((luc va) OR (duc va)) dau di cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((v nang) OR (van nang)) ma hoi. hieu qua cac ((luc va) or (duc va)) dau di cua tu".
• Adding a wildcard symbol may retrieve word variants: toc sach ((v nang) OR (van nang)) ma hoi. hieu qua cac ((luc va) or (duc va)) dau di cua tu*.