Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, vien da
tu sach » thu sach, su sach, te sach
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
y nang » ky nang, ly nang, v nang
ve cac » va cac
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan 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 y nang x hoi. hieu ((ve cac) or (vien cac)) tu va dan vi ((cuu tre) OR (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang x hoi. hieu ((ve cac) OR (vien cac)) tu va dan vi ((cuu tre) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang x hoi. hieu ((ve cac) or (vien cac)) tu va dan vi ((cuu tre) OR (cua tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang x hoi. hieu ((ve cac) or (vien cac)) tu va dan vi ((cuu tre) OR (cua tre))*.