diff --git a/src/epub/content.opf b/src/epub/content.opf
index 0052e0f..128cc74 100644
--- a/src/epub/content.opf
+++ b/src/epub/content.opf
@@ -48,7 +48,7 @@
 		</meta>
 		<dc:language>en-US</dc:language>
 		<dc:source>https://www.gutenberg.org/ebooks/19478</dc:source>
-		<dc:source>https://www.pgdp.org/ols/tools/biblio.php?id=projectID43e55dad06e70</dc:source>
+		<dc:source>https://archive.org/details/fourdayplanetlon00pipe</dc:source>
 		<meta property="se:word-count">59006</meta>
 		<meta property="se:reading-ease.flesch">73.07</meta>
 		<meta property="se:url.encyclopedia.wikipedia">https://en.wikipedia.org/wiki/H._Beam_Piper#Federation_series</meta>
diff --git a/src/epub/text/colophon.xhtml b/src/epub/text/colophon.xhtml
index 6a63133..0f71ac5 100644
--- a/src/epub/text/colophon.xhtml
+++ b/src/epub/text/colophon.xhtml
@@ -23,7 +23,7 @@
 			for<br/>
 			<a href="https://www.gutenberg.org/ebooks/19478">Project Gutenberg</a><br/>
 			and on digital scans available at the<br/>
-			<a href="https://www.pgdp.org/ols/tools/biblio.php?id=projectID43e55dad06e70">Distributed Proofreaders Open Library System</a>.</p>
+			<a href="https://archive.org/details/fourdayplanetlon00pipe">Internet Archive</a>.</p>
 			<p>The cover page is adapted from<br/>
 			<i epub:type="se:name.visual-art.painting">Cave Scene</i>,<br/>
 			a painting completed in about 1850 by<br/>
diff --git a/src/epub/text/imprint.xhtml b/src/epub/text/imprint.xhtml
index 156c5c0..4661fe4 100644
--- a/src/epub/text/imprint.xhtml
+++ b/src/epub/text/imprint.xhtml
@@ -12,7 +12,7 @@
 				<img alt="The Standard Ebooks logo" src="../images/logo.svg" epub:type="z3998:publisher-logo se:image.color-depth.black-on-transparent"/>
 			</header>
 			<p>This ebook is the product of many hours of hard work by volunteers for <a href="https://standardebooks.org">Standard Ebooks</a>, and builds on the hard work of other literature lovers made possible by the public domain.</p>
-			<p>This particular ebook is based on a transcription produced for <a href="https://www.gutenberg.org/ebooks/19478">Project Gutenberg</a> and on digital scans available at the <a href="https://www.pgdp.org/ols/tools/biblio.php?id=projectID43e55dad06e70">Distributed Proofreaders Open Library System</a>.</p>
+			<p>This particular ebook is based on a transcription produced for <a href="https://www.gutenberg.org/ebooks/19478">Project Gutenberg</a> and on digital scans available at the <a href="https://archive.org/details/fourdayplanetlon00pipe">Internet Archive</a>.</p>
 			<p>The writing and artwork within are believed to be in the <abbr>U.S.</abbr> public domain, and Standard Ebooks releases this ebook edition under the terms in the <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1.0 Universal Public Domain Dedication</a>. For full license information, see the <a href="uncopyright.xhtml">Uncopyright</a> at the end of this ebook.</p>
 			<p>Standard Ebooks is a volunteer-driven project that produces ebook editions of public domain literature using modern typography, technology, and editorial standards, and distributes them free of cost. You can download this and other ebooks carefully produced for true book lovers at <a href="https://standardebooks.org">standardebooks.org</a>.</p>
 		</section>