The First "lost" International Conference on Nonlinear Oscillations (I.C.N.O.)

From 28 to 30 January 1933 was held at the Institut Henri Poincar\'{e} (Paris) the first International Conference of Nonlinear Oscillations organized at the initiative of the Dutch physicist Balthazar Van der Pol and of the Russian mathematician Nikola\"{i} Dmitrievich Papaleksi. The discovery of this forgotten event, whose virtually no trace remains, was made possible thanks to the report written by Papaleksi at his return in USSR. This document has revealed, one the one hand, the list of participants who included French mathematicians: Alfred Li\'{e}nard, \'{E}lie and Henri Cartan, Henri Abraham, Eug\`{e}ne Bloch, L\'{e}on Brillouin, Yves Rocard, ... and, on the other hand the content of presentations and discussions. The analysis of the minutes of this conference presented here for the first time highlights the role and involvement of the French scientific community in the development of the theory of nonlinear oscillations.