Perhaps you should try some spelling variations:
toc sac » toc sach, toc san, hoc sach
nang ro » nang co, nang ra, nang rong
hieu ve » hieu va, hieu van
cuu tre » cua tre, cau tren, cau treo
nang ho » nang hoc, nang co, tang ho
sac ky » cac ky, sai ky
ve cac » va cac, vien cac
cac tu » cac thu, cach tu, cac du
va don » va dong, va doc, va do
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sac ky ((nang ho) OR (nang ro)) hoi. hieu ve cac tu va don vi ((cua te) OR (cuu tre))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sac ky ((nang ho) OR (nang ro)) hoi. hieu ve cac tu va don vi ((cua te) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: toc sac ky ((nang ho) OR (nang ro)) hoi. hieu ve cac tu va don vi ((cua te) OR (cuu tre))*.