Perhaps you should try some spelling variations:
su sach » so sach, vu sach
do caco » do cao
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ky tang » ky nang, ky dang, kho tang
cu tren » tu tren, dua tren
ma hoi » mai hoi, ma hoa, me hoi
do cac » o cac, co cac, do cao
ve am » va am
thuc » thu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky tang ((ma hoi) or (xa hoi)). hieu ve am thuc vat ((do cac) or (do caco)) cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky tang ((ma hoi) OR (xa hoi)). hieu ve am thuc vat ((do cac) OR (do caco)) cu tren.
• Adding a wildcard symbol may retrieve word variants: su sach ky tang ((ma hoi) or (xa hoi)). hieu ve am thuc vat ((do cac) or (do caco)) cu tren*.