See many mentions of the Winterburns, and brief discussions of the publication of these notes as a book, in Stockman's Notes from the National Baha'i Archives on the Chicago House of Spirituality and Notes on the Thornton Chase Papers.
This is a "Pilgrim's note," an individual's recollection of statements and actions of the Central figures. They are subjective and not authoritative. See an overview of Pilgrim's Notes.
Documents posted between 2003-2012 had slightly different URLs and can be found in archive.org with addresses like bahai-library.com/?file=winterburn_table_talks.
Documents posted prior to October 2003 were at bahai-library.org [archive.org] and had completely different URLs.