title: How to 'wait' for two observables in RxJS
body: <p>In my app i have something like:</p>
  
  <pre><code>this._personService.getName(id)
        .concat(this._documentService.getDocument())
        .subscribe((response) =&gt; {
                    console.log(response)
                    this.showForm()
         });
  
   //Output: 
   // [getnameResult]
   // [getDocumentResult]
  
   // I want:
   // [getnameResult][getDocumentResult]
  </code></pre>
  
  <p>Then i get two separated results, first of the <code>_personService</code> and then the <code>_documentService</code>. How can I wait for both results before call <code>this.showForm()</code> to finish an then manipulate the results of each one.</p>