Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
cac thuc » cach thuc, cac thu, can thuc
dang xay » dang van, van xay
cua tre » cua te, cuu tre, dua tren
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
lang xa » lang ha, lang van
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
va don » va dong, va doc, va do

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 ((lang xa) OR (dang xay)) hoi. hieu ve cac thuc va don vi ((cua tre) or (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((lang xa) OR (dang xay)) hoi. hieu ve cac thuc va don vi ((cua tre) OR (cua triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((lang xa) OR (dang xay)) hoi. hieu ve cac thuc va don vi ((cua tre) or (cua triet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((lang xa) OR (dang xay)) hoi. hieu ve cac thuc va don vi ((cua tre) or (cua triet))*.