Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
can ban » van ban, toan ban
cam ban » cac ban, cam bay, lam ban
cac xuc » cam xuc, cac nuoc, chat xuc
van cac » van hac, van cau, van bac
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
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: su sach ky ((nang x) or (nang ma)) hoi. hieu van cac xuc ((cam ban) OR (can ban)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang x) OR (nang ma)) hoi. hieu van cac xuc ((cam ban) OR (can ban)) va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang x) or (nang ma)) hoi. hieu van cac xuc ((cam ban) OR (can ban)) va cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang x) or (nang ma)) hoi. hieu van cac xuc ((cam ban) OR (can ban)) va cua tre*.