Re: 4 colours

Thanks, Richard. As you could see if you FTP-ed my note, I did quote Barry Fawcett's characterisation (and thanked Robert Pare for mentioning it to me). I also explained that Fawcett's approach is, in a sense, dual to mine. I hope I'll be able to say more about this in another note. Best regards, Dusko Pavlovic ==============================================================================