B_000 - Everything you are reading is the continuation of the work done on a file I was working on initially, which arrived at the 15th-16th version and was physically printed in three copies but of which I then lost the sources. I gave away two copies (years and years ago) and one has remained in my possession. What you find now in this series of element 'B' is an extract and rework from that booklet, much of which, however, I decided to discard.