Perhaps you should try some spelling variations:
trinh viet » ninh viet, trinh vat
dinh viet » ninh viet, danh viet, sinh vien
cau tren » cu tren, dau tren, ca tren
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
xang ma » tang ma, nang ma, sang ma
cua tre » cua te, cuu tre, cua triet
te sach » toc sach
ve cac » va cac, vien cac
dan va » doan va, dan ca, ban va
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty xang ma hoi. hieu ve cac dan va ((dinh viet) OR (trinh viet)) ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty xang ma hoi. hieu ve cac dan va ((dinh viet) OR (trinh viet)) ((cua tre) OR (cau tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty xang ma hoi. hieu ve cac dan va ((dinh viet) OR (trinh viet)) ((cua tre) or (cau tren))*".