*/
    public ArrayList<String> getBlankSignatureNames() {
        getSignatureNames();
        ArrayList<String> sigs = new ArrayList<String>();
        for (Map.Entry<String, Item> entry: fields.entrySet()) {
            Item item = entry.getValue();
            PdfDictionary merged = item.getMerged(0);
            if (!PdfName.SIG.equals(merged.getAsName(PdfName.FT)))
                continue;
            if (sigNames.containsKey(entry.getKey()))
                continue;
            sigs.add(entry.getKey());
        }
        return sigs;
    }