Perhaps you should try some spelling variations:
dang mat » dang vat, dang mau, dung mat
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
truc va » thuc va, thuc vat, trung va
hieu va » lieu va, hieu qua
hieu ve » hieu van
mat hoi » mai hoi, sat hoi, mat troi
ky dang » ky nang, ky danh
tuc va » thuc va, tuc xa, duc va
vi hoa » voi hoa, vi hoc, va hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky dang mat hoi. ((hieu ve) OR (hieu va)) cam ((tuc va) or (truc va)) hanh vi hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky dang mat hoi. ((hieu ve) OR (hieu va)) cam ((tuc va) OR (truc va)) hanh vi hoa viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky dang mat hoi. ((hieu ve) OR (hieu va)) cam ((tuc va) or (truc va)) hanh vi hoa viet".
• Adding a wildcard symbol may retrieve word variants: so sach ky dang mat hoi. ((hieu ve) OR (hieu va)) cam ((tuc va) or (truc va)) hanh vi hoa viet*.