Perhaps you should try some spelling variations:
trinh han » trinh quan
trinh tai » trinh toan, trinh tu, chinh tai
thai tuc » thai thuc, thai thuy, thai hoc
hieu van » hieu va, thien van, lieu va
van thai » van thoai, van tai, van hai
sach ky » sach y, sach ty, sach kem
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa
sac ky » cac ky, sai ky

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) nang xa hoi. hieu van thai tuc va ((trinh tai) OR (trinh han)) cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sac ky)) nang xa hoi. hieu van thai tuc va ((trinh tai) OR (trinh han)) cua tre~".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sac ky)) nang xa hoi. hieu van thai tuc va ((trinh tai) OR (trinh han)) cua tre*.