1. http://www.google.co.th/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCoQFjAA&url=http
%3A%2F%2Fwww.chs.ac.th%2FM6%2Fpre-o-net_thai6.doc&ei=xEniUf-
vL4zprQewrYDADw&usg=AFQjCNFcl3TfRh4xY39yAPnGFHy-
nI73jw&sig2=qIv6ICy7tM82oYVX8qr4MQ&bvm=bv.48705608,d.bmk
http://thaiexam.blogspot.com/2012/11/blog-post.html
http://www.dek-d.com/content/all/24336/
http://www.google.co.th/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&sqi=2&ved=0CEAQFjAC&u
rl=http%3A%2F%2Fwww.chs.ac.th%2FM6%2Fpre-o-net_soc6.doc&ei=eVXiUeeAOoGQrQf-
m4GoDw&usg=AFQjCNHgjiPbNXV85MNLzKjP9TyBV73HhA&sig2=fQKJyLfYxrHlw3zSNqQx8Q&bvm=b
v.48705608,d.bmk