Perhaps you should try some spelling variations:
su sach » so sach, vu sach
dao cao » dao tao, bao cao, tao cao
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
cu tren » tu tren, dua tren
ky sang » ky nang, ky dang, ky tang
ma hoi » mai hoi, ma hoa, me hoi
dao ca » dao cac, dao cau, dao cua
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 ((dao ca) OR (dao cao)) cu 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 ((dao ca) OR (dao cao)) cu 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 ((dao ca) OR (dao cao)) cu tren".
• Adding a wildcard symbol may retrieve word variants: su sach ky sang ((ma hoi) or (xa hoi)). hieu ve am thuc va ((dao ca) OR (dao cao)) cu tren*.