Perhaps you should try some spelling variations:
cham tuc » nham thuc, pham thuc, tham thuc
cua tre » cua te, cuu tre, cua triet
doan vi » doan va, don vi, doan thi
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
tang ma » mang may, tang van
sang ma » nang ma, sang tao, mang may
sac ky » cac ky, sai ky
tuc va » thuc va, truc va, tuc xa
dan vi » don vi, dan va, gan vi
tu sac » tu sach, tu cac, tu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky ((sang ma) or (tang ma)) hoi. hieu ve cham tuc va ((dan vi) OR (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((sang ma) OR (tang ma)) hoi. hieu ve cham tuc va ((dan vi) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((sang ma) or (tang ma)) hoi. hieu ve cham tuc va ((dan vi) OR (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((sang ma) or (tang ma)) hoi. hieu ve cham tuc va ((dan vi) OR (doan vi)) cua tre*.