Burl wrote a paper on them with a few inaccuracies . The heartland is Perthshire with others in Angis ,Kincardine and Aberdeenshire . In general the furhter from these areas the smaller they become but there are some quite bijou examples even in Perthshire . The orientations are not precise but close to the cardinal points . Long views to the south , cup marks , cremated bone deposits , cists and quartz scatters are some associations .There are some cases which have one or more low intervening slabs set neatly between the tall corner stones e.g. Lundin , Fortingall . a bit like cairn kerbing .