Perhaps you should try some spelling variations:
van thanh » ban thanh
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
thai cua » than cua, tai cuc, tri cua
van tuan » van quan, van ban, anh tuan
cua tre » cua te, cuu tre, cua triet
nang ro » nang co, nang ho, nang ra
ro lai » o lai, ho lai, ru lai
tu san » thu san, tu ban, tu can
tu sac » tu sach, tu cac, tu bac

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sac) or (tu san)) ky nang ro lai. hieu vien cac nuoc ((van thanh) OR (van tuan)) thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sac) OR (tu san)) ky nang ro lai. hieu vien cac nuoc ((van thanh) OR (van tuan)) thai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sac) or (tu san)) ky nang ro lai. hieu vien cac nuoc ((van thanh) OR (van tuan)) thai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sac) or (tu san)) ky nang ro lai. hieu vien cac nuoc ((van thanh) OR (van tuan)) thai cua tre*.