George, Thank you for posting that. I had many of the same reservations as the authors. One sticking point is the dating, by the time GT was built any memory if the YD events would have become mythical/legendary events within the oral histories of the local people, so far removed from the actual event in time, that calling it a smoking gun is somewhat of a stretch. But, that is not to say that some of the imagery does not have its genesis in an eyewitness account of the events. I disagree with their assertion that, because the buildings had roofs they could not be observatories. Newgrange and other passage tombs through out western europe are clearly observatories, as is Okmulgee in Georgia and the observatories of the meso americans all had roofs.