Perhaps you should try some spelling variations:
thuoc sac » thuoc sach, thuoc dac, thuoc sai
dung tren » dung trong, dung trung
hieu van » hieu va, thien van, lieu va
dau tren » dau tien, dat tren, dau tieng
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
va hanh » van hanh, va thanh, va danh
sac ky » cac ky, sai ky
nam tu » nam thu, nam thuc

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc sac ky ((nang xa) or (lang xa)) hoi. hieu van nam tu va hanh vi ((dung tren) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc sac ky ((nang xa) OR (lang xa)) hoi. hieu van nam tu va hanh vi ((dung tren) OR (dau tren)).
• Adding a wildcard symbol may retrieve word variants: thuoc sac ky ((nang xa) or (lang xa)) hoi. hieu van nam tu va hanh vi ((dung tren) or (dau tren))*.