diff --git a/frontend/forms.py b/frontend/forms.py
index 8f53271..cebe7f4 100644
--- a/frontend/forms.py
+++ b/frontend/forms.py
@@ -51,6 +51,7 @@ class FileUploadForm(forms.Form):
 
 
 class PersonMapForm(forms.Form):
+    """ Form containing the person mapping 'wizard'. """
     def __init__(self, *args, **kwargs):
         super(PersonMapForm, self).__init__(*args, **kwargs)
         self.helper = FormHelper()
@@ -66,6 +67,17 @@ class PersonMapForm(forms.Form):
             Submit(u'save-continue', u'Save and continue', css_class=u'btn-default'),
         )
 
+    def clean(self):
+        """ Make sure the submitted data is okay. """
+        cleaned_data = super(PersonMapForm, self).clean()
+        action = cleaned_data.get(u'action')
+        global_identity = cleaned_data.get(u'global_identity')
+        if action == u'existing' and not global_identity:
+            msg = u"Cannot map to non-existing global identity!"
+            self._errors["global_identity"] = self.error_class([msg])
+        return cleaned_data
+
     action = forms.ChoiceField(choices=[(u'new', u'Create new global Identity'), (u'existing', u'Map to existing identity')], initial=u'new', widget=forms.RadioSelect())
     global_identity = forms.ModelChoiceField(queryset=PersonGlobalIdentity.objects.all(), required=False)
     preferred_identity = forms.BooleanField(initial=False, required=False)
+
diff --git a/frontend/models.py b/frontend/models.py
index cf44497..1d0a39c 100644
--- a/frontend/models.py
+++ b/frontend/models.py
@@ -13,7 +13,7 @@ class Project(models.Model):
         if self.associated_filename:
             temp += u" (" + unicode(self.associated_filename) + u")"
         else:
-            temp += u" (empty)"
+            temp += u" (No project file)"
         return temp
 
 
@@ -24,7 +24,7 @@ class PersonGlobalIdentity(models.Model):
 
     def __unicode__(self):
         from service.Mapper import person_mapper
-        return u"<PersonGlobalIdentity repr='" + person_mapper.get_representation_for_global_identity(self) + u"', ID=" + unicode(self.id) + u", type=" + unicode(self.type) + u">"
+        return person_mapper.get_representation_for_global_identity(self) + u" [" u"ID=" + unicode(self.id) + u", Type=" + unicode(self.type) + u"]"
 
 
 class CitaviProjectIdentity(models.Model):
@@ -35,4 +35,8 @@ class CitaviProjectIdentity(models.Model):
     preferred = models.BooleanField()
 
     def __unicode__(self):
-        return u"<CitaviProjectIdentity project=" + unicode(self.project) + u", citavi_uuid=" + unicode(self.citavi_uuid) + u", global_identity=" + unicode(self.global_identity) + u", preferred=" + unicode(self.preferred) + u">"
+        from service.Mapper import person_mapper
+        citavi_repr = person_mapper.get_representation_for_citavi_identity(self)
+        if self.preferred == True:
+            citavi_repr = citavi_repr + u" <preferred>"
+        return citavi_repr
\ No newline at end of file
diff --git a/frontend/views.py b/frontend/views.py
index 316b520..3334910 100644
--- a/frontend/views.py
+++ b/frontend/views.py
@@ -12,6 +12,7 @@ from django.views.generic.detail import SingleObjectMixin
 from django.contrib.auth.decorators import login_required
 from django.utils.decorators import method_decorator
 from django.contrib.auth.views import login, logout
+from django.forms import ValidationError
 
 from frontend.forms import NewProjectForm, FileUploadForm, PersonMapForm
 
@@ -245,8 +246,7 @@ class ProjectMapPersonView(ProtectedFormView, SingleObjectMixin):
             if form.cleaned_data[u'action'] == u'new':
                 person_mapper.create_new_identity(self.object, person)
             elif form.cleaned_data[u'action'] == u'existing':
-                # TODO preferred = FALSE is not desired.
-                print form.cleaned_data
-                person_mapper.map_identity_to_existing(form.cleaned_data[u'global_identity'], self.object, person.ID, form.cleaned_data[u'preferred_identity'])
+                global_identity = form.cleaned_data[u'global_identity']
+                person_mapper.map_identity_to_existing(global_identity, self.object, person.ID, form.cleaned_data[u'preferred_identity'])
         return super(ProjectMapPersonView, self).form_valid(form)
 
diff --git a/service/Django.py b/service/Django.py
index 1f11458..990e79b 100644
--- a/service/Django.py
+++ b/service/Django.py
@@ -15,6 +15,9 @@ class PersonIdentityManager():
 
     def add_identity_to_global_identity(self, global_identity, project, uuid, preferred):
         """ Maps given citavi project identity to existing global identity. """
+        # First, fetch all involved CitaviProjectIdentities and set them to preferred=False
+        CitaviProjectIdentity.objects.filter(global_identity=global_identity).update(preferred=False)
+        # Then add the new primary ProjectIdentity.
         cpi = CitaviProjectIdentity(global_identity=global_identity, project=project, citavi_uuid=uuid, preferred=preferred)
         cpi.save()
         return cpi
diff --git a/service/Mapper.py b/service/Mapper.py
index e649369..d6bbcb6 100644
--- a/service/Mapper.py
+++ b/service/Mapper.py
@@ -60,14 +60,18 @@ class PersonMapper():
         if global_identity.type == 'citavi':
             citavi_identity = self._person_identity_manager.get_citavi_identity_by_global_identity(global_identity)
             citavi_person = self._citavi_project_manager.get_person_by_uuid(citavi_identity.project_id, citavi_identity.citavi_uuid)
-            return unicode(citavi_person.ID) + u" " + unicode(citavi_person.FirstName) + u" " + unicode(citavi_person.LastName)
+            return self._representation_for_citavi_person(citavi_person)
         else:
             return u'Not implemented yet!'
 
     def get_representation_for_citavi_identity(self, citavi_identity):
         """ Returns a unicode representation for a citavi project identiy. """
         citavi_person = self._citavi_project_manager.get_person_by_uuid(citavi_identity.project_id, citavi_identity.citavi_uuid)
-        return unicode(citavi_person.ID) + u" " + unicode(citavi_person.FirstName) + u" " + unicode(citavi_person.LastName)
+        return self._representation_for_citavi_person(citavi_person)
+
+    def _representation_for_citavi_person(self, citavi_person):
+        p = citavi_person
+        return u"<" + unicode(p.FirstName) + u" " + unicode(p.LastName) + u">"
 
 
 # Create a PersonMapper instance for public use, so ressources are not wasted.