code: public static <T> Chronology<T> lookup(Class<T> chronoType) {
  
          try {
              // Initialisierung der Klasse anstoßen, wenn noch nicht erfolgt
              Class.forName(
                  chronoType.getName(),
                  true,
                  chronoType.getClassLoader());
          } catch (ClassNotFoundException cnfe) {
              throw new IllegalStateException(cnfe);
          }
  
          Chronology<?> ret = null;
          boolean purged = false;
  
          for (ChronoReference cref : CHRONOS) {
              Chronology<?> chronology = cref.get();
  
              if (chronology == null) {
                  purged = true;
              } else if (chronology.getChronoType() == chronoType) {
                  ret = chronology;
                  break;
              }
          }
  
          if (purged) {
              purgeQueue();
          }
  
          return cast(ret); // type-safe
  
      }
docs: /*[deutsch]
  <p>Liefert ein getyptes Singleton pro {@code ChronoEntity}-Klasse. </p>
  
  @param   <T> generic type of time context
  @param   chronoType  chronological type
  @return  chronology or {@code null} if not found