Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
dang vat » dang van, dong vat, dang nhat
nam thuc » nam thuoc, am thuc, nam thu
cau theo » cau thi, cau tao
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, lang van
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan va, dan tai, dan vat
hieu va » lieu va, hieu qua
va nam » van nam, ha nam, va nay

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky ((lang xa) OR (dang xay)) hoi. hieu va nam thuc va ((dan vai) or (dang vat)) cau theo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((lang xa) OR (dang xay)) hoi. hieu va nam thuc va ((dan vai) OR (dang vat)) cau theo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky ((lang xa) OR (dang xay)) hoi. hieu va nam thuc va ((dan vai) or (dang vat)) cau theo".
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((lang xa) OR (dang xay)) hoi. hieu va nam thuc va ((dan vai) or (dang vat)) cau theo*.