Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
lang ha » long ha
hieu ca » hieu cac, hieu cua, hieu va
ky lang » ky nang, ky dang, ky tang
sach ky » sac ky, sach y, sach ty
cuu tre » cua tre, cau treo
ha hoi » hoa hoi, ha noi, xa hoi
ca nam » cua nam, cai nam, ha nam
ca dan » cac dan, ca dao
va dan » va dao, va dau, va dap

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