Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
tinh doi » trinh doc, trinh do, tinh hoc
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
cau hoc » cau hoi, cau hoa, cao hoc
va tinh » may tinh
doi cua » dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky

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 ((nang xa) or (nang ma)) hoi. ((hieu van) or (lieu va)) cau hoc va tinh doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang xa) OR (nang ma)) hoi. ((hieu van) OR (lieu va)) cau hoc va tinh doi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang xa) or (nang ma)) hoi. ((hieu van) or (lieu va)) cau hoc va tinh doi cua tre*.