Perhaps you should try some spelling variations:
trinh vi » trinh va, trinh viet, trinh van
trinh ve » trinh he, trinh va, trinh viet
hieu va » lieu va, hieu qua
nam xua » nam cua, nam mua, nam qua
cua tre » cua te, cuu tre, cua triet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
va nam » van nam, ha nam, va nay
xua va » xuat va, vua va, sua va
x hoi » xa hoi, o hoi, 5 hoi

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 ky nang ((x hoi) or (x ho)). hieu va nam xua va ((trinh vi) OR (trinh ve)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang ((x hoi) OR (x ho)). hieu va nam xua va ((trinh vi) OR (trinh ve)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky nang ((x hoi) or (x ho)). hieu va nam xua va ((trinh vi) OR (trinh ve)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang ((x hoi) or (x ho)). hieu va nam xua va ((trinh vi) OR (trinh ve)) cua tre*.