The user can control the algorithm through SIC variables. New values 
can be given using "LET VARIABLE value". For ease of use, and whenever 
it is possible, a sensible value of each parameter will automatically 
be computed from the context if the value of the corresponding variable 
is set to its default value, i.e. zero value and empty string. A few 
variables are initialized to "reasonable" values.

.ti +4
[CLEAN_\]CLEAN ?
.br 
Will list all main CLEAN__* variables controlling the CLEAN parameters
for the current METHOD.

HELP CLEAN Variables will give a more complete list.
