Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
danh ve » dinh ve, hanh ve, anh ve
va danh » va dinh, va dan, va hanh
thuc va » thuc vat, thuc dan, thuc day
cu tren » tu tren, dua tren
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
x hoi » o hoi, x ho, 5 hoi
ve cu » ve cau, ve chu, ve cua

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

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