Credit/Permission:
©
Joaquim Alves Gaspar (AKA User:Alvesgaspar)
,
2008
/
Public domain
.
Image link:
Wikimedia Commons: File:DopplerTrain.jpg
.
Credit/Permission: ©
Joaquim Alves Gaspar
(AKA User:Alvesgaspar),
2008 /
Public domain.