diff --git a/zip-0400.rst b/zip-0400.rst
index 6edcc286..cae16002 100644
--- a/zip-0400.rst
+++ b/zip-0400.rst
@@ -28,7 +28,7 @@ The process of saving wallet data into disk is currently unspecified. The key-va
 Specification
 =============
 
-Zcash stores wallet information in a Berkeley database(BDB) commonly known as wallet.dat. 
+Zcash stores wallet information in a Berkeley database(BDB) [#BDB]_ commonly known as wallet.dat. 
 The main purpose of this is the persistence of public and private keys the user created and the ability to recover the wallet state after a node restart. This file also allows the migration of user information from one node to another by moving the database to the corresponding new datadir assuming both zcashd instances are running the same or similar version. Additional features like encryption, recovery, etc are also implemented.
 
 The current database is a key-value store where keys and values can have multiple data types in binary format. The first data found in a database key is always the property name, the rest of the key is generally used to identify a record, for example::
@@ -166,6 +166,7 @@ References
 ==========
 
 .. [#RFC2119] `Key words for use in RFCs to Indicate Requirement Levels <https://www.rfc-editor.org/rfc/rfc2119.html>`_
+.. [#BDB] `Oracle Berkeley Database <https://www.oracle.com/database/berkeley-db/db.html>`_
 .. [#ZIP400Attempt] `ZIP 400 initial attempt <https://github.com/leto/zips/blob/d279728cc457a824abb6dec1fc560ab9c7a9a510/zip-0400.rst>`_
 .. [#ZIP400Issue] `ZIP 400 issue <https://github.com/zcash/zips/issues/350>`_
 .. [#CrypterCode] `Database key encryption implementation <https://github.com/zcash/zcash/blob/master/src/wallet/crypter.h>`_