Perhaps you should try some spelling variations:
sang ma » tang ma, sang tao, mang may
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, nang cao, mang may
tuc va » thuc va, truc va, duc va
dan vi » doan vi, don vi, dan va
vi cua » vai cua, di cua

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

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