synchronized (_sheet) {
if (_refs != null && !_refs.isEmpty()) {
final Set<Ref> all = new HashSet<Ref>();
for (Ref ref : _refs) {
if (ref.isWholeRow()) {
final RefSheet refSheet = ref.getOwnerSheet();
final Worksheet sheet = BookHelper.getSheet(_sheet, refSheet);
final int tRow = ref.getTopRow();
final int bRow = ref.getBottomRow();
final Set<Ref> refs = BookHelper.setRowsHidden(sheet, tRow, bRow, hidden);
all.addAll(refs);
} else if (ref.isWholeColumn()) {
final RefSheet refSheet = ref.getOwnerSheet();
final Worksheet sheet = BookHelper.getSheet(_sheet, refSheet);
final int lCol = ref.getLeftCol();
final int rCol = ref.getRightCol();
final Set<Ref> refs = BookHelper.setColumnsHidden(sheet, lCol, rCol, hidden);
all.addAll(refs);