Perhaps you should try some spelling variations:
nhieu viec » nhien viet
hieu viec » hieu ve, sieu viet, hieu hien
toc sach » hoc sach, doc sach, thuoc sach
dang mat » dang vat, dang mau, dung mat
sach thu » sach thue, sach thieu, sach tham
dat xuc » dat nuoc, dat duoc, chat xuc
dang ma » dang mau, dang mam, tang ma
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
xuc va » duc va, tuc va, luc va
o viet » so viet, hoc viet
va o » va co, va do, va mo

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 thu ((dang ma) or (dang mat)) hoi. ((hieu viec) OR (nhieu viec)) dat xuc va hanh va o viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thu ((dang ma) OR (dang mat)) hoi. ((hieu viec) OR (nhieu viec)) dat xuc va hanh va o viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach thu ((dang ma) or (dang mat)) hoi. ((hieu viec) OR (nhieu viec)) dat xuc va hanh va o viet".
• Adding a wildcard symbol may retrieve word variants: toc sach thu ((dang ma) or (dang mat)) hoi. ((hieu viec) OR (nhieu viec)) dat xuc va hanh va o viet*.