Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau treo » cau tren, cau triet, cau trieu
cau theo » cau thi, cau tao
lang ha » long ha
lang xa » dang xay, lang van
sach ky » sac ky, sach y, sach ty
dao vai » dao van, dao va, dao bai
hieu va » lieu va, hieu qua
va nam » van nam, ha nam, va nay
thu va » thuc va, thue va, tu va
va dao » ca dao

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 ky ((lang xa) or (lang ha)) hoi. hieu va nam thu va dao vai ((cau treo) OR (cau theo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((lang xa) OR (lang ha)) hoi. hieu va nam thu va dao vai ((cau treo) OR (cau theo)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky ((lang xa) or (lang ha)) hoi. hieu va nam thu va dao vai ((cau treo) OR (cau theo))".
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((lang xa) or (lang ha)) hoi. hieu va nam thu va dao vai ((cau treo) OR (cau theo))*.