diff --git a/dev/js/spec/vcSpec.js b/dev/js/spec/vcSpec.js
index 5e813aa..f657ee9 100644
--- a/dev/js/spec/vcSpec.js
+++ b/dev/js/spec/vcSpec.js
@@ -1732,6 +1732,96 @@
       vc = vcClass.create().fromJson(nested);
       expect(vc.wasRewritten()).toBeTruthy();
     });
+
+    it('should add document at virtual corpus', function () {
+      vc = vcClass.create();
+      expect(vc.toQuery()).toEqual("");
+
+      let doc = docClass.create();
+      doc.key("author");
+      doc.type("string");
+      doc.matchop("eq");
+      doc.value("Goethe");
+      expect(doc.toQuery()).toEqual('author = "Goethe"');
+
+      expect(vc.element().firstChild.children.length).toEqual(1);
+      expect(vc.element().firstChild.firstChild.classList.contains("unspecified")).toBeTruthy();
+
+      vc.addRequired(doc);
+      expect(vc.toQuery()).toEqual('author = "Goethe"');
+
+      expect(vc.element().firstChild.children.length).toEqual(1);
+      expect(vc.element().firstChild.firstChild.classList.contains("doc")).toBeTruthy();
+
+      // Add as 'and' to doc
+      let doc2 = docClass.create();
+      doc2.key("author");
+      doc2.type("string");
+      doc2.matchop("eq");
+      doc2.value("Schiller");
+      vc.addRequired(doc2);
+      expect(vc.toQuery()).toEqual('author = "Goethe" & author = "Schiller"');
+
+      expect(vc.element().firstChild.firstChild.classList.contains("docGroup")).toBeTruthy();
+      expect(vc.element().firstChild.firstChild.children[0].classList.contains("doc")).toBeTruthy();
+      expect(vc.element().firstChild.firstChild.children[1].classList.contains("doc")).toBeTruthy();
+
+      
+      // Add as 'and' to 'and'-docGroup
+      let doc3 = docClass.create();
+      doc3.key("author");
+      doc3.type("string");
+      doc3.matchop("eq");
+      doc3.value("Fontane");
+      vc.addRequired(doc3);
+      expect(vc.toQuery()).toEqual('author = "Goethe" & author = "Schiller" & author = "Fontane"');
+
+      expect(vc.element().firstChild.firstChild.classList.contains("docGroup")).toBeTruthy();
+      expect(vc.element().firstChild.firstChild.children[0].classList.contains("doc")).toBeTruthy();
+      expect(vc.element().firstChild.firstChild.children[1].classList.contains("doc")).toBeTruthy();
+      expect(vc.element().firstChild.firstChild.children[2].classList.contains("doc")).toBeTruthy();
+
+      // Add as 'and' to 'or'-docGroup
+      vc = vcClass.create().fromJson({
+        "@type" : 'koral:docGroup',
+        'operation' : 'operation:or',
+        'operands' : [
+          {
+            '@type' : 'koral:doc',
+            'key' : 'title',
+            'value' : 'Hello World!'
+          },
+          {
+            '@type' : 'koral:doc',
+            'key' : 'foo',
+            'value' : 'bar'
+          }
+        ]
+      });
+      expect(vc.toQuery()).toEqual('title = "Hello World!" | foo = "bar"');
+
+      let doc4 = docClass.create();
+      doc4.key("author");
+      doc4.type("string");
+      doc4.matchop("eq");
+      doc4.value("Fontane");
+      vc.addRequired(doc4);
+      expect(vc.toQuery()).toEqual('(title = "Hello World!" | foo = "bar") & author = "Fontane"');
+
+      // Add as 'and' to 'or'-docGroup
+      vc = vcClass.create().fromJson({
+        "@type" : "koral:docGroupRef",
+        "ref" : "@max/myCorpus"
+      })
+      let doc5 = docClass.create();
+      doc5.key("author");
+      doc5.type("string");
+      doc5.matchop("eq");
+      doc5.value("Goethe");
+      expect(doc5.toQuery()).toEqual('author = "Goethe"');
+      vc.addRequired(doc5);
+      expect(vc.toQuery()).toEqual('referTo "@max/myCorpus" & author = "Goethe"');
+    });
   });
 
 
diff --git a/dev/js/src/vc.js b/dev/js/src/vc.js
index d2029d0..7494cdf 100644
--- a/dev/js/src/vc.js
+++ b/dev/js/src/vc.js
@@ -413,6 +413,48 @@
       }
     },
 
+    // Add "and" constraint to VC
+    addRequired : function (doc) {
+
+      let root = this.root();
+      let ldType = root.ldType();
+
+      let parent = root.parent();
+      if (ldType === 'non') {
+        parent.root(doc);
+      }
+
+      // root is doc
+      else if (
+        ldType === 'doc' ||
+          ldType === 'docGroupRef' ||
+          (ldType === 'docGroup' &&
+           root.operation() === 'or'
+          )) {
+        let group = require('vc/docgroup').create(
+          parent
+        );
+        group.operation("and");
+        group.append(root);
+        group.append(doc);
+        group.element(); // Init (seems to be necessary)
+        parent.root(group);
+      }
+      
+      // root is a docGroup
+      // and is already an 'and'-Group
+      else if (ldType === 'docGroup') {
+        root.append(doc);
+      }
+
+      // Unknown
+      else {
+        console.log("Unknown root object");
+      };
+
+      // Init element and update
+      this.update();
+    },
     
     /**
      * Get the generated json string