Josupeit, Stefan, et al. “Powder Ageing and Material Properties of Laser Sintered Polyamide 12 Using Low Refresh Rates.”10.1007/978-3-662-48473-9_5__Proceedings of the Rapid Tech 2015, Springer Vieweg, 2015, pp. 63–78, doi:10.1007/978-3-662-48473-9_5.