Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
thuoc va » thuc va, thuoc ma, thuong va
dau tren » dau tien, dat tren, dau tieng
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
va nam » van nam, ha nam, va nay
va dan » ca dan, va dao, va dap
dan va » doan va, dan ca, ban va
va dau » va dao

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

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