Standardise on sentence case for titles
diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 1d76817..164d0ab 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -1,4 +1,4 @@
-Test Vectors
+Test vectors
 ============
 
 Testing the correctness of the primitives implemented in each ``cryptography``
@@ -10,7 +10,7 @@
 Sources
 -------
 
-Asymmetric Ciphers
+Asymmetric ciphers
 ~~~~~~~~~~~~~~~~~~
 
 * RSA PKCS #1 from the RSA FTP site (ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/
@@ -43,7 +43,7 @@
 * HMAC-RIPEMD160 from :rfc:`2286`.
 * HMAC-SHA2 (224, 256, 384, 512) from :rfc:`4231`.
 
-Key Derivation Functions
+Key derivation functions
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 * HKDF (SHA1, SHA256) from :rfc:`5869`.
@@ -55,7 +55,7 @@
 
 * Fernet from its `specification repository`_.
 
-Symmetric Ciphers
+Symmetric ciphers
 ~~~~~~~~~~~~~~~~~
 
 * AES (CBC, CFB, ECB, GCM, OFB) from `NIST CAVP`_.
@@ -72,14 +72,14 @@
 * IDEA (CBC, CFB, OFB) generated by this project.
   See: :doc:`/development/custom-vectors/idea`
 
-Two Factor Authentication
+Two factor authentication
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 * HOTP from :rfc:`4226`
 * TOTP from :rfc:`6238` (Note that an `errata`_ for the test vectors in RFC
   6238 exists)
 
-Creating Test Vectors
+Creating test vectors
 ---------------------
 
 When official vectors are unavailable ``cryptography`` may choose to build