Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau tren » dau tren, ca tren, cau treo
nam thuc » nam thuoc, am thuc, nam thu
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
sach ty » sach y, sach tu, sach thu
cu tren » tu tren, dua tren
hieu va » lieu va, hieu qua
lang ha » long ha
lang xa » dang xay, lang van
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 ty ((lang xa) or (lang ha)) hoi. hieu va nam thuc va dan vai ((cau tren) OR (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty ((lang xa) OR (lang ha)) hoi. hieu va nam thuc va dan vai ((cau tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty ((lang xa) or (lang ha)) hoi. hieu va nam thuc va dan vai ((cau tren) OR (cu tren))".
• Adding a wildcard symbol may retrieve word variants: toc sach ty ((lang xa) or (lang ha)) hoi. hieu va nam thuc va dan vai ((cau tren) OR (cu tren))*.