Analysis of information sources in references of the Wikipedia article "Reporting mark (ferrovia)" in Portuguese language version.
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(ajuda)McGonigal, Robert S. (May 1, 2006). "Understanding railroad reporting marks". Trains. Archived from the original on 2014-10-27. Retrieved 2014-12-09.|data=
(ajuda)McGonigal, Robert S. (May 1, 2006). "Understanding railroad reporting marks". Trains. Archived from the original on 2014-10-27. Retrieved 2014-12-09.