diff --git a/Failing-PDFs.md b/Failing-PDFs.md
index 4dec8c7..e7bdd95 100644
--- a/Failing-PDFs.md
+++ b/Failing-PDFs.md
@@ -6,6 +6,7 @@ The following tags are used to specify why they break:
 * FONT: breaking due to not fully supported fonts
 * RENDERING: breaking due to not jet implemented rendering spec
 * THROW: throws an error while doing the rendering
+* INVALID: invalid PDF structure
 
 From issue [#560](https://github.com/andreasgal/pdf.js/issues/560):
 
@@ -13,9 +14,9 @@ From issue [#560](https://github.com/andreasgal/pdf.js/issues/560):
 
 From issue [#577](https://github.com/andreasgal/pdf.js/issues/577):
 
-* ???: https://docs.rice.edu/confluence/download/attachments/4588376/unix01.pdf?version=1
-* ???: www-csag.ucsd.edu/~jburke/Vesta/Vesta_Overview.pdf
-* ???: http://www.csb.yale.edu/userguides/graphics/rasmol/rasmol.pdf
-* ???: people.csail.mit.edu/ledlie/papers/tr-03-02.pdf
-* ???: www.nsa.gov/ia/_files/app/pdf_risks.pdf
-* ???: www.mit.edu/~6.033/writing-samples/usmanm_dp1.pdf
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+* FONT(no spaces): https://docs.rice.edu/confluence/download/attachments/4588376/unix01.pdf?version=1
+* THROW(RGBT command?): www-csag.ucsd.edu/~jburke/Vesta/Vesta_Overview.pdf
+* FONT(no spaces): http://www.csb.yale.edu/userguides/graphics/rasmol/rasmol.pdf
+* RENDERING(2d graphics),THROW: people.csail.mit.edu/ledlie/papers/tr-03-02.pdf
+* RENDERING(JPX): www.nsa.gov/ia/_files/app/pdf_risks.pdf
+* INVALID: www.mit.edu/~6.033/writing-samples/usmanm_dp1.pdf
\ No newline at end of file