- One typescript attendance list and announcement list w. annots.; all lvs. (sl.) yellowed.
= Signatories include E.P. Hubble, Th. von Kármán, J.M. Burgers, H.C. van de Hulst, J.H. Oort, A. Blaauw, O. Laporte, H.W. Liepmann, G.K. Batchelor, D.W. Sciama, L. Biermann and H. Bondi.
Attendance sheet, International Union of Theoretical and Applied Mechanics, London, September 1948, 2 typescript lvs. listing council members' names and addresses, 2 lvs. w. AUTOGRAPH participants' names (pen and ink/ ballpoint).
= Signatories include J. Pérès, Th. von Kármán, S.P. Timoshenko, C.B. Biezenmo, J.M. Burgers and H. Favre.
Attendance sheets, International Union of Theoretical and Applied Mechanics, Istanbul, August 21-26, 1952, 6 typescript lvs. w. AUTOGRAPH participants' names (pencil/ pen and ink/ ballpoint).
= Signatories include J.C. Hunsaker, S.P. Timoshenko, R. von Mises, F.H. van den Dungen, C.B. Biezenmo, J.M. Burgers and H. Favre.
AND 3 other members' attendants' lists, i.a. for the "International symposium on nonlinear vibrations", Île de Porquerolles, 18-22 September 1951 (6 (yellowed) (facs.) typescript lvs., 1 leaf w. annots.). - ADDED: 1 postcard, w. postmark dated "14 Ap[ril] 4[8?]", by "R.S." (R.V. Southwell?) addressed to Prof. J.M. Burgers.