Perhaps you should try some spelling variations:
nang hoc » nang doc, nang luc, dong hoc
cua tre » cua te, cuu tre, cua triet
nang ra » nang ma, lang ra, nang ro
hieu ve » hieu va, hieu van
vi cua » vai cua, di cua
cac tu » cac thu, cach tu, cac du
ve cac » va cac, vien cac
sac ky » cac ky, sai ky
va do » va dao, va doc, va co
do vi » don vi, doc vi, do voi

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) or (sach y)) ((nang hoc) or (nang ra)) hoi. hieu ve cac tu va do vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sac ky) OR (sach y)) ((nang hoc) OR (nang ra)) hoi. hieu ve cac tu va do vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sac ky) or (sach y)) ((nang hoc) or (nang ra)) hoi. hieu ve cac tu va do vi cua tre*.