http://www.chicagotribune.com/suburbs/post-tribune/news/ct-ptb-porter-propane-buses-st-0730-story.html
https://www.tmpropane.com/
http://www.waaytv.com/content/news/Franklin-County-Schools-get-new-fleet-of-propane-fueled-buses-482703171.html
https://kobi5.com/news/propane-fueled-heater-may-have-caused-structure-fire-in-josephine-county-62619/