how to validate if there is atleast one checkbox is selected out of 3 checkbox in angularjs for mvc

                            <input name="chkbx1" type="checkbox"
                                ng-model="LoanReferData.Prop1"
                                ng-class="Submitted?'ng-dirty':''" required>Prop 1</input>

                            <input name="chkbx2" type="checkbox"
                                ng-model="LoanReferData.Prop2" ng-class="Submitted?'ng-dirty':''"
                                required>Prop 2</input>

                            <input name="chkbx3" type="checkbox" ng-model="LoanReferData.Prop3"
                                ng-class="Submitted?'ng-dirty':''" required>Other</input>

* please select atleast 1 property is required.