<!doctype html>
<html ng-app>
  <head>
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.4/angular.min.js"></script>
  </head>
  <body>
  <!-- BAD -->
  <a href="{{help_url}}">Help</a>
  <picture>
    <source media="(min-width: 650px)" srcset="#/resources/pics-large/{{item._id}}">
    <img src="#/resources/pics-default/{{item._id}}">
  </picture> 
  <!-- GOOD -->
  <a ng-href="{{help_url}}">Help</a>
  <picture>
    <source media="(min-width: 650px)" ng-srcset="#/resources/pics-large/{{item._id}}">
    <img ng-src="#/resources/pics-default/{{item._id}}">
  </picture> 
  </body>
</html>