Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, gian cac
hanh tri » thanh tri, hanh tai, hanh trinh
van hanh » van thanh, ban hanh, van anh
nuoc van » nuoc va, nuoc san, luoc van
vien da » vien dai, hien dai
sach ky » sach y, sach ty, sach kem
nang co » nang cao, nang doc, nang noi
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc, co loi
sac ky » cac ky, sai ky

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) OR (sac ky)) nang co hoi. hieu ((vien cac) or (vien da)) nuoc van hanh tri cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) nang co hoi. hieu ((vien cac) OR (vien da)) nuoc van hanh tri cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) OR (sac ky)) nang co hoi. hieu ((vien cac) or (vien da)) nuoc van hanh tri cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) OR (sac ky)) nang co hoi. hieu ((vien cac) or (vien da)) nuoc van hanh tri cua tre*.