Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
su triet » su viet, su tien, ve triet
sach thu » sach thue, sach thieu, sach tham
nang xa » nang x, lang xa, mang xa
sach tu » cach tu, sach ty, sach uu
thuc va » thuc vat, thuc dan, thuc day
nang ma » tang ma, sang ma, nang cao
va dau » va dao
dau ki » dau khi, du ki
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach tu) OR (sach thu)) ((nang xa) or (nang ma)) hoi. hieu van nam thuc va dau ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach tu) OR (sach thu)) ((nang xa) OR (nang ma)) hoi. hieu van nam thuc va dau ki su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach tu) OR (sach thu)) ((nang xa) or (nang ma)) hoi. hieu van nam thuc va dau ki su triet".
• Adding a wildcard symbol may retrieve word variants: thu ((sach tu) OR (sach thu)) ((nang xa) or (nang ma)) hoi. hieu van nam thuc va dau ki su triet*.