On 4 October 1960, Preparatory Commission President, Cardinal Fernando Cento, wrote Cardijn and other commission members informing them of their first meeting including a special audience with Pope John XXIII on Sunday 14 November.
He also invited them to take the oath of secrecy before the Apostolic Delegate or Nuncio.
A second letter also invited him to send his “observations and suggestions, not necessarily in Latin.”
Subjects
Also enclosed were other documents listing the subjects to be dealt with along with the other members of the Commission and the Sub-Commissions to which they had been allocated.
This was evidently sent out in Latin but Cardijn had had it translated into French.

Members of the Sub-Commissions
Cardijn thus found himself appointed to Sub-Commission I, which was to deal with Notions relating to Catholic Associations and Catholic Action.

SOURCES
Original Latin plus rough English translation
Cardinal Cento to PCLA Members 1960 10 04 (Joseph Cardijn Digital Library)
Cardinal Cento to Cardijn 1960 10 04 – 02 (Joseph Cardijn Digital Library)
Other Documents
Archives Cardijn 1584