Quote by Martin Niemoeller

First they came for the Communists but I was not a Communist so I did not speak out.
Then they came for the Socialists and the Trade Unionists but I was not one of them, so I did not speak out.
Then they came for the Jews but I was not Jewish so I did not speak out.
And when they came for me, there was no one left to speak out for me.

Please suggest source details if you know: book, page, year, online article address (url), correction (different author...), etc.. Thanks.