 Going back to Formula 2, calculation of the thermal contact conductance may prove difficult, even impossible, due to the difficulty in measuring the contact area, formula_4 (A product of surface characteristics, as explained earlier).Because of this, contact conductance/resistance is usually found experimentally, by using a standard apparatus.The results of such experiments are usually published in Engineering literature, on journals such as "Journal of Heat Transfer", "International Journal of Heat and Mass Transfer", etc.