Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien bac » vien bach, vien cac, mien bac
tu sach » thu sach, te sach, tu cach
cua tre » cua te, cua triet, dua tren
danh va » doanh va, hanh va, anh va
va danh » va dinh, va dan, va hanh
bac cao » bao cao, bac can, bac cau
su sach » so sach, vu sach
cuu tre » cau tren, cau treo
cao va » cao van, tao va, co va
x hoi » xa hoi, o hoi, x ho

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 x hoi. hieu vien bac cao va danh va ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang x hoi. hieu vien bac cao va danh va ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky nang x hoi. hieu vien bac cao va danh va ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky nang x hoi. hieu vien bac cao va danh va ((cua tre) OR (cuu tre))*.