Perhaps you should try some spelling variations:
danh kien » dinh kien, danh viet, linh kien
doc sach » hoc sach, toc sach, nuoc sach
kien cua » khien cua, dien cua, tien cua
thuc day » thuc dan, thuc vat
thuc va » thuc vat, thuc dan
va tham » van tham, va cham, va thanh
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet

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

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