Referenced in the IBM Systems Journal, my 1999 MA essay on tangible computing, focusing on the work of Durrell Bishop, is still available by request. Often cited in PhD work on related subjects, the essay was cited in Brygg Ullmer and Hiroshi Ishii’s paper, Emerging Frameworks for Tangible Interfaces, by (IBM SJ, Volume 39, Issue 3-4, July 2000, pp 915-931). You’re welcome to email to request a copy. If you refer to this work in your own research or publications, please reference the source appropriately. See also Durrell’s own web site for further documentation of his projects, ideas and research.