Long term study had been done where electronic pain diary were compared against paper diary in recording pain in 36 patients with chronic low back pain. The 2 scales showed good correlation. This author use a software that is Palm-top computer based. Following these few studies, validation study in chronic pain patient were published. A Palm-top computer based VAS was compared with paper NRS in 200 chronic pain patients. The pain level recorded by the two methods were considered equivalent by the author. However, Palm-top computer has almost disappeared from the market nowadays.