Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
tinh doi » trinh doc, trinh do, tinh hoc
tu sach » thu sach, su sach, te sach
doi cua » dai cua, hoi cua, dong cua
van lam » van nam
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa

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 ((nang xa) or (nang x)) hoi. hieu van lam ((tuc va) or (thuc vat)) tinh doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang x)) hoi. hieu van lam ((tuc va) OR (thuc vat)) tinh doi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (nang x)) hoi. hieu van lam ((tuc va) or (thuc vat)) tinh doi cua tre*.