bing	bing
crossref	crossref
ddg	duckduckgo
duckduckgo	duckduckgo
github	github
google	google
google_scholar	google_scholar
qwant	qwant
rdoc	rdocumentation
rdocumentation	rdocumentation
rdrr	rdrr_io
rdrr_io	rdrr_io
reddit	reddit
r_bloggers	r_bloggers
so	stackoverflow
stackoverflow	stackoverflow
twitter	twitter
web	web
wikipedia	wikipedia
wolfram	wolframalpha
wolframalpha	wolframalpha
wp	wikipedia
