Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
hanh tai » thanh tai, hang tai, han tai
tai cua » thai cua, tai cuc, tri cua
van cam » van nam, van lam, van cau
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
tuc va » thuc va, truc va, duc va
cua tu » cua tuc, cua su, cua cu

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

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