https://en.wikipedia.org/wiki/Hillsborough_disaster
https://doi.org/10.1016/0925-7535(94)00034-Z
https://doi.org/10.1061/(ASCE)0733-947X(2005)131:8(575)
https://www.theguardian.com/football/2016/apr/26/hillsborough-disaster-deadly-mistakes-and-lies-that-lasted-decades