Selected papers."A conference with the title 'Partial Differential Equations of Elliptic Type' was held in Cortona, Italy, from October 12 to October ...
"A conference with the title 'Partial Differential Equations of Elliptic Type' was held in Cortona, Italy, from October 12 to October 16, 1922 [i.e. 1992]." -- foreword.