angular circular dependency

acd.js

angular.module("app", [])
     .service('A', function(B) {
         this.data1 = 'a';
         this.foo = function() {
             console.log('A.foo:', this.data1, B.data2);
         }
     })
     .service('B', function(A) {
         this.data2 = 'b';
         this.foo = function() {
             console.log('B.foo:', A.data1, this.data2);
         }
     })
     .run(function(A, B) {
         A.foo();
         B.foo();
     });