Perhaps you should try some spelling variations:
cau tren » cu tren, ca tren, cau treo
dau tren » dau tien, dat tren, dau tieng
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach kem
cau luc » cau truc, cau phuc
hieu ve » hieu va, hieu van
ma hoi » mai hoi, xa hoi, ma hoa
ve cau » ke cau, va cau, ve cac
luc va » duc va, tuc va, loc va
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

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 ky) or (sach ty)) nang ma hoi. hieu ve cau luc va dan vi ((cau tren) OR (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((sach ky) OR (sach ty)) nang ma hoi. hieu ve cau luc va dan vi ((cau tren) OR (dau tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((sach ky) or (sach ty)) nang ma hoi. hieu ve cau luc va dan vi ((cau tren) OR (dau tren))*".