Representative res estimate for no-PDF (yellow) study; author preference unknowable. Value -1.15 confirmed against Dahl DEDD ref ESC73 (El-r IR -1.15); Dahl cross-check CONFIRMED.
Erickson, E.W., R.M. Spann, and R. Ciliano (1973): “Substitution and Usage in Energy Demand: An Econometric Estimation of Long-Run and Short-Run Effects.” In: Energy Modeling: Art, Science, Practice (ed. M. F. Searl), Resources for the Future, Inc., Washington D.C.