Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
nam xua » nam cua, nam mua, nam qua
nam xuc » cam xuc, nam thuc, nam duoc
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
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: tu sach ky ((nang ma) OR (tang ma)) hoi. hieu van ((nam xuc) or (nam xua)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang ma) OR (tang ma)) hoi. hieu van ((nam xuc) OR (nam xua)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang ma) OR (tang ma)) hoi. hieu van ((nam xuc) or (nam xua)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang ma) OR (tang ma)) hoi. hieu van ((nam xuc) or (nam xua)) van hanh vi cua tre*.