Perhaps you should try some spelling variations:
nhieu vien » nhieu viec, nhiet dien, thieu nien
vien cac » vien bach, vien dai, vien da
trinh he » trinh han, trinh hoa, trinh thi
trinh de » trinh den, trinh do, trinh di
cac duc » cac du, cao duc, cac dac
duc lap » doc lap, duc lai, duc lam
tu sach » thu sach, te sach, tu cach
nang ma » tang ma, sang ma, nang cao
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet

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 (su sach)) ky nang ma hoa. nhieu vien cac duc lap ((trinh de) OR (trinh he)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang ma hoa. nhieu vien cac duc lap ((trinh de) OR (trinh he)) cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky nang ma hoa. nhieu vien cac duc lap ((trinh de) OR (trinh he)) cua tre*".