--- a/TODO	Wed May 17 12:10:27 2017 +0100
+++ b/TODO	Fri Jun 23 00:27:53 2017 +0100
@@ -1,5 +1,7 @@
+Not-regular expressions & derivatives
+http://www.dcc.fc.up.pt/dcc/Pubs/TReports/TR13/dcc-2013-11.pdf
 
-
+http://www.home.hs-karlsruhe.de/~suma0002/publications/cc14-flexible-lexing-via-extended-regex.pdf
 
 Regular Path Queries & regular expressions
 
@@ -23,3 +25,7 @@
 http://www.arl.wustl.edu/~pcrowley/
 http://regex.wustl.edu/index.php/Regular_Expression_Processor
 
+
+
+Contextfree expressions
+https://arxiv.org/pdf/1610.06832.pdf
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