• Reference spectroscopy. It is interesting to note that in 2013 there is a pick in the graph, probably this is the year when BIM became more important. there is also some reference to articles very old:  LANGLEY B. (1756) THE CITY AND COUNTRY BUILDER'S AND WORKMAN'S TREASURY OF DESIGNS OR THE ART OF DRAWING AND WORKING THE ORNAMENTAL PARTS OF ARCHITECTURE. S. HARDING LONDON  and MEYMOTT W. (1774) AN ABRIDGEMENT OF SUCH PART OF THE BUILDING ACT (PASSED IN THE YEAR 1774) AS WILL BE USEFUL TO ALL PERSONS LONDON: J. BROWN   Those two articles do not seem very connected to BIM, probably they are in the same paper and serve some purpose. Probably they're not interesting for BIM research.