title: Sass: how to manage blank space inside a single string of an array
body: <p>I need to insert <code>'Roboto', sans-serif</code> as a single string of an array.
  I tried something like that:</p>
  
  <p><code>$p: (2vw 4vw 3vw 4.5vw 'Roboto'+,sans-serif)</code></p>
  
  <p>but it doesn't work.
  Any suggestion?
  Thanks</p>