Links:
[1] https://www.digi-sign.com/downloads/download.php?id=aacd-digi-ssl-pdf
[2] https://www.digi-sign.com/aacd/certificate+service+gateway
[3] https://www.digi-sign.com/aacd/daemon+server+side+application
[4] https://www.digi-sign.com/digi-ca
[5] https://www.digi-sign.com/certificate+authority