Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
cuu tre » cua tre, cau tren, cau treo
duc van » duc va, duc tan, duc manh
cao duc » dao duc, cao suc, giao duc
van cao » van dao, van bao, van hao
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa

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 ky ((nang xa) or (nang ma)) hoi. hieu van cao duc van hanh vi ((cuu tre) or (cau thi))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang ma)) hoi. hieu van cao duc van hanh vi ((cuu tre) OR (cau thi)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (nang ma)) hoi. hieu van cao duc van hanh vi ((cuu tre) or (cau thi))*.