«What are MD2, MD4, and MD5?»(en anglès).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. Arxivat de l'original el 2011-09-01.[Consulta: 29 abril 2011].
«What are MD2, MD4, and MD5?»(en anglès).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. Arxivat de l'original el 2011-09-01.[Consulta: 29 abril 2011].