It was done almost 40 years ago [0]. It never caught on, though I'm sure there were a few people who liked it. [0] http://dspace.mit.edu/bitstream/handle/1721

It was done almost 40 years ago [0]. It never caught on, though I'm sure there were a few people who liked it. [0] http://dspace.mit.edu/bitstream/handle/1721.1/41951/AI_WP_121.pdf?sequence=1 http://dspace.mit.edu/bitstream/handle/1721.1/41951/AI_WP_12...