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