Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
khoa hoi » khoan hoi, khoa hoc, khoa doi
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
hoa hoi » hoa hoc, hoa doi, hoc hoi
ky lang » ky nang, ky dang, ky tang
vai su » van su, lai su, tai su
ve nam » he nam, va nam, le nam

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 lang ((hoa hoi) or (khoa hoi)). hieu ve nam thuc va hanh ((vai su) OR (va su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang ((hoa hoi) OR (khoa hoi)). hieu ve nam thuc va hanh ((vai su) OR (va su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang ((hoa hoi) or (khoa hoi)). hieu ve nam thuc va hanh ((vai su) OR (va su)) triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ((hoa hoi) or (khoa hoi)). hieu ve nam thuc va hanh ((vai su) OR (va su)) triet*.