http://www.get-music.net/chart/us-top-40.html

http://top40-charts.com/chart.php?cid=27

http://www.bbc.co.uk/radio1/chart/singles.shtml

http://www.top40-charts.com/

http://www.get-music.net/chart/uk-top-40.html

http://top10songschart.com/Top-40-Chart-Music.html

http://www.at40.com/rest_chart.html?format=chr&

http://en.wikipedia.org/wiki/Top_40_(radio_format)

http://www.rianz.org.nz/rianz/chart.asp

http://www.take40.com/

http://en.wikipedia.org/wiki/Top_40

http://top40.about.com/

http://www.billboard.com/bbcom/charts/chart_display.jsp?g=Singles&f=The+Billboard+Hot+100

http://www.americasmusiccharts.com/index.cgi?fmt=H1

http://www.theofficialcharts.com/top40_singles.php

http://docquinn_1.tripod.com/top40tracknotes.html

http://www.bbc.co.uk/radio1/chart/

http://acharts.us/world_singles_top_40

http://www.eightyeightynine.com/music/top40.html

http://www.bigtop40.com/chart/