Add refs

Author: srvanderplas

_freeze/part-wrangling/04-strings/execute-results/html.json

@@ -522,6 +522,8 @@ I've assembled a [YouTube playlist](https://www.youtube.com/embed/videoseries?li
 
 The following demonstrations are intended for advanced students: if you are just learning how to program, you may want to come back to these when you need them.
 
+There is also an excellent site which helps you learn regular expressions via interactive tutorials, @regexoneRegexOne. Another useful tool is @leaverouRegExplained2017
+
 ::: {.callout-advanced collapse="true"}
 ### Regular Expression Basics
 

part-wrangling/04-strings.qmd

@@ -1477,3 +1477,23 @@ @online{anishathalyeMissingSemesterYour
 	langid = {english},
 	file = {Snapshot:/home/susan/.Zotero/storage/HHW6269T/missing.csail.mit.edu.html:text/html},
 }
+
+@online{regexoneRegexOne,
+	title = {{RegexOne}},
+	url = {https://regexone.com/},
+	author = {{RegexOne}},
+	urldate = {2023-04-20},
+	file = {RegexOne - Learn Regular Expressions - Lesson 1\: An Introduction, and the ABCs:/home/susan/.Zotero/storage/AHBRJ7WW/regexone.com.html:text/html},
+}
+
+
+@online{leaverouRegExplained2017,
+	title = {Reg Explained},
+	url = {https://projects.verou.me/regexplained/},
+	titleaddon = {/a(b)/g},
+	author = {{Lea Verou}},
+	urldate = {2023-04-20},
+	date = {2017},
+	file = {RegExp playground:/home/susan/.Zotero/storage/HTD8Q3HA/regexplained.html:text/html},
+}
+