Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
cau treo » cau theo, cau triet, cau trieu
cau tren » cu tren, dau tren, ca tren
sach ty » sach y, sach tu, sach thu
thuc ca » thuc cua, thuc can, thuc cao
dan vai » dan va, dan tai, dan vat
ty nang » ky nang, ty xang, ty hang
va nam » van nam, va nay
ca dan » cac dan, ca dao
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ty nang x hoi. hieu ((va nam) or (ha nam)) thuc ca dan vai ((cau treo) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty nang x hoi. hieu ((va nam) OR (ha nam)) thuc ca dan vai ((cau treo) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ty nang x hoi. hieu ((va nam) or (ha nam)) thuc ca dan vai ((cau treo) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: doc sach ty nang x hoi. hieu ((va nam) or (ha nam)) thuc ca dan vai ((cau treo) OR (cau tren))*.