code: public Source setSource(String url) {
  		Source property = (url == null) ? null : new Source(url);
  		setSource(property);
  		return property;
  	}
docs: Sets the location that the calendar data can be refreshed from.
  @param url the source or null to remove
  @return the property object that was created
  @see <a
  href="http://tools.ietf.org/html/draft-ietf-calext-extensions-01#page-8">draft-ietf-calext-extensions-01
  p.8</a>