Update README.md

Author: Alizamin Jafarli

README.md

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 # JavaScript (JS)
 JavaScript often abbreviated as JS, is a high-level, interpreted scripting language that conforms to the ECMAScript specification. JavaScript has curly-bracket syntax, dynamic typing, prototype-based object-orientation, and first-class functions.  Alongside HTML and CSS, JavaScript is one of the core technologies of the World Wide Web. JavaScript enables interactive web pages and is an essential part of web applications.
 
-# MUST:
+# MUST: https://www.evernote.com/shard/s386/u/0/sh/679872e6-9ee1-4d49-9029-b57f7749fcd5/0bdd9f06f48635a3130a5c9d07779bd1
 <ul>
       <li>Book: <a href="https://github.com/HackTechGO/You-Dont-Know-JS">You Don't Know Javascript</a></li>
       <li><a href="https://github.com/HackTechGO/fundamentals">JS Fundamentals</a></li>
@@ -11,6 +11,7 @@ JavaScript often abbreviated as JS, is a high-level, interpreted scripting langu
             <li><a href="https://www.bitdegree.org/learn/nodelist#nodelist-main-tips">NodeList vs. HTMLCollection</a></li>
             <li><a href="https://www.nikpro.com.au/javascript-nodelist-and-html-dom-collection-and-how-to-use-them/">Javascript NodeList and HTML DOM collection and how to use them </a></li>
              <li><a href="https://www.evernote.com/shard/s386/u/0/sh/af2449fc-c9de-4334-9328-f5c215ea93ba/fee416e4cf8f9f6e13f8427973eedbda"> JavaScript: What the heck is a Callback? </a></li>
+              <li><a href="https://www.evernote.com/shard/s386/u/0/sh/679872e6-9ee1-4d49-9029-b57f7749fcd5/0bdd9f06f48635a3130a5c9d07779bd1"> What is AJAX and How Does It Work? </a>, <a href="https://www.w3schools.com/whatis/whatis_ajax.asp">w3schools</a> and <a href="https://developer.mozilla.org/en-US/docs/Web/Guide/AJAX/Getting_Started">MDN</a></li>
       </ul>
       <li><a href="https://www.youtube.com/watch?v=y3itGTCseAk">Nodes Versus Elements in the DOM </a> (Recommend to get subscribed to his channel as well)</li>