https://www.google.com/search?q=nsalert+error+icon&client=firefox-b&tbm=isch&source=iu&ictx=1&fir=2iRctS5fJByN0M%253A%252Cw324MTzjHa1bAM%252C_&usg=__x3wpwdNN1L8VI2kHtkKAXFMtpj4%3D&sa=X&ved=0ahUKEwjJzpjN2qDZAhVjw1kKHfOHDoQQ9QEIMTAB#imgrc=2iRctS5fJByN0M:
http://0xced.blogspot.com/2009/11/clalert-nsalert-done-right.html
https://gist.github.com/0xced/228140
http://editra.org/uploads/code/artmac.html
http://mirror.informatimago.com/next/developer.apple.com/documentation/Carbon/Reference/IconServices/index.html
http://www.cocoabuilder.com/archive/cocoa/15427-iconref-to-nsimage.html
https://github.com/lukakerr/Swift-NSUserNotificationPrivate
https://stackoverflow.com/questions/32943220/the-sidebar-icon-image-name-in-osx