A comprehensive introduction to PCT and its implications for the social and physical environment, on a global scale, are described in an online article by Kent McClelland. There are also a number of online articles that relate PCT to environmental issues: e.g. Lenk (2009), Lengevin et al. (2015) & Lengevin et al. (2014). These include applications to maintaining homeland security and applying counter-terrorism measures (Bank, 2002) and applications for water conservation (Henderson, 2016).
