<p style="font-size: 12px;color:#aaa;">版权引用：<a href="https://avopix.com/photo/386595-zig-zag-passenger-and-freight-train-by-an-unknown-artist-original-from-library-of-congress"><span style="font-size: 12px;color:black;">“Zig-zag Passenger and Freight Train by an unknown artist. Original from Library of Congress.”</span> </a>由 <a href="https://avopix.com/author/photos/library-of-congress-source"><span style="font-size: 12px;color:black;">Library of Congress (Source)</span></a> 授权许可 <span><a href="https://creativecommons.org/publicdomain/zero/1.0/deed.zh" target="_blank" style="font-size: 12px;color:black;">CC0 1.0 Universal Public Domain Dedication<img src="" style="display: inline-block;height: 16px;width: auto;"></a></span></p>