Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
mai viet » thi viet
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
va viet » hoa viet, san viet, dao viet
sach ty » sach y, sach tu, sach thu
thuc va » thuc vat, thuc dan, thuc day
sang ma » tang ma, nang ma, sang tao
ty sang » ty xang, ty hang, duy sang
co viet » so viet, o viet, hoc viet
ma hoi » mai hoi, xa hoi, ma hoa
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

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 sang ma hoi. hieu van nam thuc va dan vi ((((va viet) OR (mai viet))) or (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty sang ma hoi. hieu van nam thuc va dan vi ((((va viet) OR (mai viet))) OR (co viet))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty sang ma hoi. hieu van nam thuc va dan vi ((((va viet) OR (mai viet))) or (co viet))*".