2 

     2 

     3 \usepackage{amsmath,amssymb,amsthm}

     3 \usepackage{amsmath,amssymb,amsthm}

     4 

     4 

     5 \usepackage[all]{xy}

     5 \usepackage[all]{xy}

     6 

     6 

     8 

     8 

     9 %%%%% excerpts from my include file of standard macros

     9 %%%%% excerpts from my include file of standard macros

    10 

    10 

    11 \def\bc{{\cal B}}

    11 \def\bc{{\cal B}}

    12 

    12