The only Boolean functions accepted in this format are conjunctions of
literals, called terms. A term has the following syntax:
[-]<var> ... [-]<var> 0
where <var> is a variable and '-' in front of a <var> makes it a negative literal and no '-' in front of <var> makes it a positive literal. There are no commas in the variable list and the list is terminated with a 0. Variables may appear in a variable list in any order and are separated by blank characters.