derived from the event's own title: "Neville's 1949 Milwaukee lecture series"

passage 538537 (lecture nid 1375), 'As a result of this in 1941, it was 1949 that I gave a series of lectures in Milwaukee'

passage 540176 (lecture nid 1457), 'I made a commitment to give a series of lectures in Milwaukee on the first of May', combined with the year 1949 stated in passage 538537 for the same series (this event, per npr history of the 7420 merge)