*{{Citation | last1=Gelfand | first1=I. M. | last2=Gindikin | first2=S. G. | last3=Graev | first3=M. I. | title=Selected topics in integral geometry | publisher=[[American Mathematical Society]] | location=Providence, R.I. | series=Translations of Mathematical Monographs | isbn=978-0-8218-2932-5 | year=2003 | volume=220 | mr=2000133}} | *{{Citation | last1=Gelfand | first1=I. M. | last2=Gindikin | first2=S. G. | last3=Graev | first3=M. I. | title=Selected topics in integral geometry | publisher=[[American Mathematical Society]] | location=Providence, R.I. | series=Translations of Mathematical Monographs | isbn=978-0-8218-2932-5 | year=2003 | volume=220 | mr=2000133}} |