HP 20b
- http://www.nnar.org/archives/576
- http://www.july.co.jp/index.php?main_page=product_info&products_id=274
- http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareIndex.jsp?lang=en&cc=us&prodNameId=3732535&prodTypeId=215348&prodSeriesId=3732534&swLang=13&taskId=135&swEnvOID=54
- http://yamada-radio-clinic.cocolog-nifty.com/blog1/2008/10/hp20b-dbb9.html