void RemoveReference(IPersonReference reference)
{
References.Remove(reference);
PatternWords.Remove(reference);
NominativePersons.Remove(reference);
ReferencesSelectedItem = null;
UpdateLookup(null);
}
void UpdatePersonHeaders()
{
ErrorsVisibility = PatternWords.Any() ? Visibility.Visible : Visibility.Collapsed;
NominativesVisibility = NominativePersons.Any() ? Visibility.Visible : Visibility.Collapsed;
}