Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
cac thuc » cach thuc, cac thu, can thuc
dua tren » dung tren
van thuc » va thuc, dan thuc, van thu
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach y, sach ty
va hang » van hang, va nang, va lang
hang di » hang doi, hang vi, hang dien
ky lang » ky nang, ky dang, ky tang
cuu tre » cua tre, cau tren, cau treo

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky lang xa hoi. hieu ve ((cac thuc) or (van thuc)) va hang di ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky lang xa hoi. hieu ve ((cac thuc) OR (van thuc)) va hang di ((dua tren) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: thu sach ky lang xa hoi. hieu ve ((cac thuc) or (van thuc)) va hang di ((dua tren) or (cuu tre))*.