Perhaps you should try some spelling variations:
van khanh » van thanh, van hanh, van anh
cau theo » cau thi, cau tao
khanh ke » thanh ke, khanh kiem, thanh ket
sach thu » sach thue, sach thieu, sach tham
thuc van » thuc vat, thuc dan, thuc va
cam thuc » am thuc, nam thuc, cam thu
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
va cam » va cham, va cac, va cao
ke cau » ket cau
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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