Here is the right description:

1) A, ..., Z, TRUE, FALSE - are correct boolean expressions;

2) if x and y are correct boolean expressions, then the correct boolean expressions are also:
  (x);  NOT x;  x AND y;  x OR y  (maybe, with some extra spaces).

Edited by author 19.09.2007 23:19

It's not completely true, some spaces also may be missed as in example.