Perhaps you should try some spelling variations:
nang cau » nang cao, hang cau, nang dau
hieu van » hieu va, thien van, lieu va
thuc dan » thuc hanh, hoc dan, thuc vat
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc day
cua cau » cua cac, cua chu, cua cay
ca cau » cac cau, can cau, ca cac

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 nang cau hoi. hieu van nam ((thuc va) OR (thuc dan)) dan ((ca cau) or (cua cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang cau hoi. hieu van nam ((thuc va) OR (thuc dan)) dan ((ca cau) OR (cua cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang cau hoi. hieu van nam ((thuc va) OR (thuc dan)) dan ((ca cau) or (cua cau)) tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang cau hoi. hieu van nam ((thuc va) OR (thuc dan)) dan ((ca cau) or (cua cau)) tren*.