Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
trinh do » trinh ky
tinh doi » trinh doc, tinh hoc, tinh son
cua tre » cuu tre, cua triet, dua tren
thuc va » thuc vat, thuc dan, thuc day
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
sach o » sach lo, sac o, sach y
ve nam » he nam, va nam, le nam
o lang » hoa lang, hoi lang
cua te » cua tu

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 o lang xa hoi. hieu ve nam thuc va ((tinh doi) OR (trinh do)) ((cua tre) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach o lang xa hoi. hieu ve nam thuc va ((tinh doi) OR (trinh do)) ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach o lang xa hoi. hieu ve nam thuc va ((tinh doi) OR (trinh do)) ((cua tre) or (cua te))".
• Adding a wildcard symbol may retrieve word variants: toc sach o lang xa hoi. hieu ve nam thuc va ((tinh doi) OR (trinh do)) ((cua tre) or (cua te))*.