Source 1: http://mikeventrice.weebly.com/mjo.html
Source 2: https://www.geo.fu-berlin.de/en/met/ag/strat/produkte/qbo/index.html
Source 3: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml
Source 3 and 5: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml
Source 4: https://acd-ext.gsfc.nasa.gov/Data_services/met/qbo/qbo.html