Ιn the Archive of Dr Nikolaos Mavris which is kept at the American School of Classical Studies / Gennadeios Library, one can find his correspondence with George N. Papanicolaou. Most of these letters are referring to the contribution of both men in the Presiding board of the organization: “ National Committee for the Restoration of Greece” during the period of the Italian and German Possession of Greece (1940-44).
http://www.ascsa.edu.gr/index.php/archives/mavris-finding-aid
Additionaly in this Archive is also stored a letter of George N. Papanicolaou addressed to the distinguished Greek diplomat, Jonas Dragoumis .
http://dragoumis.ascsa.net/id/dragoumis/letter/1793?q=%CF%80%CE%B1%CF%80%CE%B1%CE%BD%CE%B9%CE%BA%CE%BF%CE%BB%CE%AC%CE%BF%CF%85&t=&v=list&sort=&s=1