Long-Delayed Echoes - Radio Society of Great Britain - Main Site : Radio Society of Great Britain – Main Site
Possible observations and mechanism of very long delayed radio echoes - Crawford - 1970 - Journal of Geophysical Research (1896-1977) - Wiley Online Library
Light Echoes Give Clues to Protoplanetary Disk
LDE
EPSILON BOÖTIS REVISITED – The Orkney News
The Five Most Likely Explanations for Long Delayed Echoes - Department of Physics