1.00 original draft by GG, May 1996, following discussion with RE 1.10 revised by GG, October 1996, following meeting with RE, BK, NN \& CR. 1.11 revised by RE, November 1996. 1.20 LaTeX/HTML version by DG, incorporating email from JK, January 1997. 2.00 revised by GG, August 1998, following detailed discussion with RE and comments from JC and BK. 2.01 revised by GG, October 1998, notes of earlier debate removed from visible text (though retained as comments in LaTeX source).
2.20 revised by RE & GG, November 1998, mostly the same as 2.01 but the treatment of metalevel nodes is greatly improved in the light of five new primitive functions (and one old function with a new name).