Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » dau tren, ca tren, cau treo
thuc day » thuc dan, thuc vat
sach thu » sach thue, sach thieu, sach tham
dan vai » dan va, dan tai, dan vat
day dan » day danh, dao dan, cay dan
cu tren » tu tren, dua tren
hieu va » lieu va, hieu qua
long ha » dong ha, cong ha, dong hoa
lang xa » lang ha, dang xay, lang van
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 thu ((lang xa) or (long ha)) hoi. hieu va nam thuc day dan vai ((cau tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thu ((lang xa) OR (long ha)) hoi. hieu va nam thuc day dan vai ((cau tren) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: toc sach thu ((lang xa) or (long ha)) hoi. hieu va nam thuc day dan vai ((cau tren) or (cu tren))*.