Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nha thuoc, cay thuoc
vat hanh » vat thanh, van hanh, va hanh
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
nang xa » nang x, lang xa, nang ma
sac ky » cac ky, sai ky
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ty) or (sac ky)) nang xa hoi. hieu ve ((nam thuoc) OR (nam thu)) vat hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sac ky)) nang xa hoi. hieu ve ((nam thuoc) OR (nam thu)) vat hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) or (sac ky)) nang xa hoi. hieu ve ((nam thuoc) OR (nam thu)) vat hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sac ky)) nang xa hoi. hieu ve ((nam thuoc) OR (nam thu)) vat hanh di cua tre*.