using multiple states with app.single

Hi I just want to know if I can use multiple states with app.single. My app shows blank when adding another state using app.single, but if I remove it the app shows again.

app.js
.state('app.checkin', {
      url: "/checkin",
      views: {
        'menuContent': {
          templateUrl: "templates/checkin.html",
          controller: 'CheckinCtrl'
        }
      }
    })

  .state('app.single', {
    url: "/checklist",
    views: {
      'menuContent': {
        templateUrl: "templates/checklist.html",
        controller: 'ChecklistCtrl'
      }
    }
  })

  .state('app.single', {
    url: "/checkekstra",
    views: {
      'menuContent': {
        templateUrl: "templates/checkekstra.html",
        controller: 'CheckekstraCtrl'
      }
    }
  });

let me know if my question is vague, thank you.