In graph theory the incidence function that associates vertices & edges, in the text it has following notation http://books.google.co.uk/books?id=HuDFMwZOwcsC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false at page 2

Question

anonymous · Answer

what do we call to this notation?

turingtest · Answer

so tiny...
is it just$$\huge\psi$$?

turingtest · Answer

oh I see what you mean...
the Greek letter is lower case psi, and I do not know any name for that particular notation, though I know practically nothing of graph theory

anonymous · Answer

thanks @TuringTest