Merge Tim Keller's Sermon Archives

I have four resources with Tim Keller's sermons: The Timothy Keller Sermon Archive The Timothy Keller Sermon Archive, 2012-2013 The Timothy Keller Sermon Archive, 2014=2015 The Timothy Keller Sermon Archive, 2016-2017 Right now, each resource has their own indices called Sermons by Date, Sermons by Series, Sermons by Reference. If they could be merged into one resource, these indices could also be unified. It would be much more user friendly.