https://www.google.co.th/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjTobH7hsHYAhXJNI8KHbBKC2AQFggpMAA&url=http%3A%2F%2Fwww.finearts.cmu.ac.th%2Fe_doc%2F52%2Fkreakjaksan%25202.pdf&usg=AOvVaw2-wt09GcneXVbwGGDF4ElURead less