diff --git a/Additional-Learning-Resources.md b/Additional-Learning-Resources.md
index 2474d9b..ddd54c2 100644
--- a/Additional-Learning-Resources.md
+++ b/Additional-Learning-Resources.md
@@ -28,9 +28,8 @@ A really basic overview of PDF is described here:
 Summary of the PDF file format:
 + http://www.planetpdf.com/developer/article.asp?ContentID=navigating_the_internal_struct
 
-The PDF specification itself:
-+ http://www.adobe.com/devnet/acrobat/pdfs/PDF32000_2008.pdf
-+ http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/pdf_reference_1-7.pdf
+The PDF specification:
++ https://www.adobe.com/devnet/acrobat/pdfs/PDF32000_2008.pdf
 
 Presentations:
 + http://labs.appligent.com/files/2013/03/recognizing_malformed_pdf_f.pdf