Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cau tren » cu tren, ca tren, cau treo
cham tuc » nham thuc, pham thuc, tham thuc
ve cham » va cham, ve chat, vu cham
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
hieu ve » hieu va, hieu van
tuc va » thuc va, truc va, tuc xa
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: tu sach ky ((sang ma) or (nang ma)) hoi. hieu ve cham tuc va dan vi ((cau tren) OR (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((sang ma) OR (nang ma)) hoi. hieu ve cham tuc va dan vi ((cau tren) OR (dau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((sang ma) or (nang ma)) hoi. hieu ve cham tuc va dan vi ((cau tren) OR (dau tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((sang ma) or (nang ma)) hoi. hieu ve cham tuc va dan vi ((cau tren) OR (dau tren))*.