Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van cham » van chat, van tham, va cham
doan vi » doan va, don vi, doan thi
truc va » thuc va, thuc vat, trung va
cuu tre » cua tre, cau tren, cau treo
mau hoi » cau hoi, mai hoi, mau hop
ky dang » ky nang, ky danh
sac ky » cac ky, sai ky
mau ho » mau hop, mau co, mau do
vi cuu » vi luu, vinh cuu
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 dang ((mau hoi) OR (mau ho)). hieu van cham ((truc va) or (tuc xa)) doan vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky dang ((mau hoi) OR (mau ho)). hieu van cham ((truc va) OR (tuc xa)) doan vi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky dang ((mau hoi) OR (mau ho)). hieu van cham ((truc va) or (tuc xa)) doan vi cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky dang ((mau hoi) OR (mau ho)). hieu van cham ((truc va) or (tuc xa)) doan vi cuu tre*.