"What are MD2, MD4, and MD5?". Public-Key Cryptography Standards (PKCS): PKCS #7: Cryptographic Message Syntax Standard: 3.6 Other Cryptographic Techniques: 3.6.6 What are MD2, MD4, and MD5?. RSA Laboratories. Archived from the original on 2011-09-01. Retrieved 2011-04-29.
"What are MD2, MD4, and MD5?". Public-Key Cryptography Standards (PKCS): PKCS #7: Cryptographic Message Syntax Standard: 3.6 Other Cryptographic Techniques: 3.6.6 What are MD2, MD4, and MD5?. RSA Laboratories. Archived from the original on 2011-09-01. Retrieved 2011-04-29.