Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ho » nang hoc, nang co, tang ho
nang ro » nang co, nang rong, nang cao
nang ra » nang ma, lang ra, nang va
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
cac tu » cac thu, cach tu, cac du
va don » va dong, va doc, va do
vi cua » vai cua, di cua

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