Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
thuc va » thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
ky sang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
ma hoi » mai hoi, ma hoa, me hoi
dao ca » dao cac, dao cao, dao cau
ca cau » cua cau, cac cau, can cau
ve am » va am

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 sang ((ma hoi) or (xa hoi)). hieu ve am ((thuc va) OR (thuc vat)) dao ca cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky sang ((ma hoi) OR (xa hoi)). hieu ve am ((thuc va) OR (thuc vat)) dao ca cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky sang ((ma hoi) or (xa hoi)). hieu ve am ((thuc va) OR (thuc vat)) dao ca cau tren".
• Adding a wildcard symbol may retrieve word variants: su sach ky sang ((ma hoi) or (xa hoi)). hieu ve am ((thuc va) OR (thuc vat)) dao ca cau tren*.