--- a/handouts/ho01.tex	Fri May 06 13:15:52 2016 +0100
+++ b/handouts/ho01.tex	Wed Jun 01 13:04:06 2016 +0100
@@ -9,6 +9,24 @@
 %%https://www.reddit.com/r/ProgrammingLanguages/comments/42dlem/mona_compiler_development_part_2_parsing/
 %%https://www.reddit.com/r/ProgrammingLanguages/comments/43wlkq/formal_grammar_for_csh_tsch_sh_or_bash/
 
+%% regex displayers
+%% https://regexper.com/#a%7Ca
+%% https://www.debuggex.com
+%% https://jex.im/regulex/#!embed=false&flags=&re=%5E(a%7Cb)*%3F%24
+
+%% email validator
+%% http://www.ex-parrot.com/%7Epdw/Mail-RFC822-Address.html
+
+%% regex testers
+% https://regex101.com
+% http://regexr.com
+
+%% emacs regexes
+%% https://www.gnu.org/software/emacs/manual/html_node/elisp/Regular-Expressions.html
+
+%% reasons for a new prgramming language
+%% http://beautifulracket.com
+
 \begin{document}
 \fnote{\copyright{} Christian Urban, King's College London, 2014, 2015, 2016}