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