}
private Set<IEctsConversionTable> processEnrolmentByInstitutionStatus(EctsTableFilter filter) {
final Unit ist = UnitUtils.readInstitutionUnit();
Set<IEctsConversionTable> tables = new HashSet<IEctsConversionTable>();
EctsConversionTable table = EctsTableIndex.readOrCreateByYear(filter.getExecutionInterval()).getEnrolmentTableBy(ist);
if (table != null) {
tables.add(table);
} else {
tables.add(new NullEctsConversionTable(ist));
}