Perhaps you should try some spelling variations:
van thang » van thanh, van khang, van hang
nam thuc » nam thuoc, am thuc, nam thu
thuc van » thuc vat, thuc dan, thuc va
sach ky » sac ky, sach ty, sach kem
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
ve nam » he nam, va nam, le nam
doi su » oi su, voi su
don su » dong su, down su, dan su

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 ky) or (sach y)) lang xa hoi. hieu ve nam thuc van thang ((doi su) OR (don su)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach y)) lang xa hoi. hieu ve nam thuc van thang ((doi su) OR (don su)) viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach y)) lang xa hoi. hieu ve nam thuc van thang ((doi su) OR (don su)) viet*".