\magnification=1200 \hsize=4in \overfullrule=0pt \input amssym %\def\frac#1 #2 {{#1\over #2}} \def\emph#1{{\it #1}} \def\em{\it} \nopagenumbers \noindent % % {\bf A.D. Forbes, M.J. Grannell and T.S. Griggs} % % \medskip \noindent % % {\bf Steiner Triple Systems and Existentially Closed Graphs} % % \vskip 5mm \noindent % % % % We investigate the conditions under which a Steiner triple system can have a 2- or 3-existentially closed block intersection graph. \bye .