Perhaps you should try some spelling variations:
nhieu vien » nhieu viec, nhiet dien, thieu nien
trinh he » trinh han, trinh hoa, trinh thi
trinh ve » trinh va, trinh vi, trinh viet
vien cac » vien bach, vien dai, vien da
cac duc » cac du, cao duc, cac dac
tu sach » thu sach, su sach, te sach
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
so sach » so sanh, bo sach, co sach
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (so sach)) ky tang ma hoi. nhieu vien cac duc va ((trinh ve) OR (trinh he)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (so sach)) ky tang ma hoi. nhieu vien cac duc va ((trinh ve) OR (trinh he)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (so sach)) ky tang ma hoi. nhieu vien cac duc va ((trinh ve) OR (trinh he)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (so sach)) ky tang ma hoi. nhieu vien cac duc va ((trinh ve) OR (trinh he)) cua tre*.