Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
lang ha » long ha
lang xa » dang xay, lang van
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
cau luc » cau truc, cau phuc
cua tre » cua te, cuu tre, cua triet
luc va » duc va, tuc va, loc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc sach ky ((lang xa) OR (lang ha)) hoi. hieu van cau luc va ((hanh tai) or (hanh vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc sach ky ((lang xa) OR (lang ha)) hoi. hieu van cau luc va ((hanh tai) OR (hanh vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc sach ky ((lang xa) OR (lang ha)) hoi. hieu van cau luc va ((hanh tai) or (hanh vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: thuoc sach ky ((lang xa) OR (lang ha)) hoi. hieu van cau luc va ((hanh tai) or (hanh vi)) cua tre*.