Perhaps you should try some spelling variations:
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cac dac » cac dan, cac dai, cac bac
danh vi » dinh vi, danh di, danh va
cua tre » cua te, cuu tre, cua triet
dac va » duc va, day va, dat va

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 va cac dac va ((danh vi) OR (hanh vi)) 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 va cac dac va ((danh vi) OR (hanh vi)) 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 va cac dac va ((danh vi) OR (hanh vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang x) or (nang ma)) hoi. hieu va cac dac va ((danh vi) OR (hanh vi)) cua tre*.