Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hanh vai » hanh va, hanh tai, hanh van
cua viet » ca viet, hoa viet, cua vat
duy sang » duy van, duy can, duy anh
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu va, hieu van
cau tuc » cau truc, cau tu, cau luc
y sang » _ sang
tuc va » thuc va, truc va, tuc xa
ve cau » ke cau, va cau, ve cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ((y sang) or (duy sang)) mai hoi. hieu ve cau tuc va ((hanh vai) OR (hanh vi)) cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((y sang) OR (duy sang)) mai hoi. hieu ve cau tuc va ((hanh vai) OR (hanh vi)) cua viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((y sang) or (duy sang)) mai hoi. hieu ve cau tuc va ((hanh vai) OR (hanh vi)) cua viet*".