Major Soviet Maritime Ports, Airports, and Sea Routes, 1986.
<a href="//commons.wikimedia.org/wiki/Library_of_Congress" title="Library of Congress"><img alt="Library of Congress" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Seal_of_the_United_States_Library_of_Congress.svg/22px-Seal_of_the_United_States_Library_of_Congress.svg.png" decoding="async" width="22" height="22" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Seal_of_the_United_States_Library_of_Congress.svg/33px-Seal_of_the_United_States_Library_of_Congress.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Seal_of_the_United_States_Library_of_Congress.svg/44px-Seal_of_the_United_States_Library_of_Congress.svg.png 2x" data-file-width="720" data-file-height="720"></a> Edited by Raymond E. Zickel, <a href="https://en.wikipedia.org/wiki/Federal_Research_Division" class="extiw" title="w:Federal Research Division">Federal Research Division</a>, Library of Congress, Washington, D.C. 20540.
<a rel="nofollow" class="external text" href="http://www.marines.mil/Portals/59/Publications/Soviet%20Union%20Study_8.pdf">Soviet Union: A country study</a> (Second Edition, First Printing, 1991,) Chapter 14. Transportation and Communications, page 574.