Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
sach thu » sach thue, sach thieu, sach tham
tan hanh » tan thanh, tang hanh, toan hanh
hanh va » hang va, hanh vi
cam duc » cam xuc, cao duc, pham duc
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
nang xa » lang xa, nang ma, mang xa
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua

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