Here is a list of the sources included. Please suggest sources in the comments field:
americanheritage.com
bbc.co.uk
bbchistorymagazine.com
brevitymag.com/
businessweek.com
cironline.org
cjr.org
creativenonfiction.org
csmonitor.com
eagle.brooklynpubliclibrary.org
economist.com
esquire.com
ft.com
garev.uga.edu/
gq.com/
granta.com/
grist.org
guardian.co.uk
harpers.org/
hcn.org
historytoday.com
inthesetimes.com
laphamsquarterly.org/
latimes.com
lifehacker.com/
longform.org
longreads.com
mercurynews.com
motherjones.com
narrative.ly/
narrativemagazine.com
nationalgeographic.com
newrepublic.com/
newsweek.com
newyorker.com
niemanlab.org/
niemanstoryboard.org/
nplusonemag.com/
npr.org
nybooks.com/
nytimes.com
outsideonline.com
progressive.org
propublica.org
prospect.org
pshares.org
riverteethjournal.com/
sacbee.com
salon.com
sfgate.com
signonsandiego.com
smithsonianmag.com
telegraph.co.uk/
texasmonthly.com
theatlantic.com
theatlantic.com
themayborn.com
thenation.com
thesunmagazine.org/
time.com
tnr.com
usnews.com
utne.com
vanityfair.com
villagevoice.com
washingtonpost.com
wired.com
wsj.com