this article, ffl the library reference TARSKI:2 indicates the second theorem in the article TARSKI, ffl the library reference BOOLE:def 1 indicates the first definitional theorem in the article BOOLE. 2. When referring to a schema we write from identifier-of-schema (% 1 , ... , %n ); where % 1 , ... , %n are references, if the schema has premises, or from identifier-of-schema ; if the schema has no premises. EXAMPLES ex Z st x holds x 2 X iff x 2 X & x 2 Y from Separation; thus thesis from FuncEx (A1,A2); The words Separation and FuncEx are identifiers of schemes, while A1, A2 are labels of the sentences which are premises, that is assumptions of the schema FuncEx