Ó Ceallaigh, S. T., & O'Brien, W. (1919). Copy and partial copy of letter from Seán T. Ó Ceallaigh to William O'Brien introducing him Mr. Frank P. Walsh of New York, Chairman of the American Commission on Irish Independence, requesting O'Brien organise for him to meet all prominent labour workers during his time in Ireland and also informing him he has become well-acquainted with his brother Thomas John O'Brien.

Ó Ceallaigh, Seán T., and William O'Brien. Copy and Partial Copy of Letter from Seán T. Ó Ceallaigh to William O'Brien Introducing Him Mr. Frank P. Walsh of New York, Chairman of the American Commission on Irish Independence, Requesting O'Brien Organise for Him to Meet All Prominent Labour Workers During His Time in Ireland and Also Informing Him He Has Become Well-acquainted with His Brother Thomas John O'Brien. 1919.