Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hai trac » hoi trac, khai thac, thai tran
hai truc » dai truc, hang truc, thai thuc
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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

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