Minor documentation fixes
diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index c833d72..94a5e0a 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -360,7 +360,7 @@
  * If a key is created with psa_import_key() and then exported with
  * this function, it is not guaranteed that the resulting data is
  * identical: the implementation may choose a different representation
- * of the same key.
+ * of the same key if the format permits it.
  *
  * For standard key types, the output format is as follows:
  *
@@ -370,7 +370,7 @@
  *   correct.
  * - For Triple-DES, the format is the concatenation of the
  *   two or three DES keys.
- * - For RSA key pairs keys (#PSA_KEY_TYPE_RSA_KEYPAIR), the format
+ * - For RSA key pairs (#PSA_KEY_TYPE_RSA_KEYPAIR), the format
  *   is the non-encrypted DER representation defined by PKCS\#8 (RFC 5208)
  *   as PrivateKeyInfo.
  * - For RSA public keys (#PSA_KEY_TYPE_RSA_PUBLIC_KEY), the format
@@ -385,6 +385,7 @@
  *
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_EMPTY_SLOT
+ * \retval PSA_ERROR_NOT_PERMITTED
  * \retval PSA_ERROR_COMMUNICATION_FAILURE
  * \retval PSA_ERROR_HARDWARE_FAILURE
  * \retval PSA_ERROR_TAMPERING_DETECTED
@@ -403,7 +404,7 @@
 
 /** The type of the state data structure for multipart hash operations.
  *
- * This is an implementation-define \c struct. Applications should not
+ * This is an implementation-defined \c struct. Applications should not
  * make any assumptions about the content of this structure except
  * as directed by the documentation of a specific implementation. */
 typedef struct psa_hash_operation_s psa_hash_operation_t;
@@ -609,7 +610,7 @@
 
 /** The type of the state data structure for multipart MAC operations.
  *
- * This is an implementation-define \c struct. Applications should not
+ * This is an implementation-defined \c struct. Applications should not
  * make any assumptions about the content of this structure except
  * as directed by the documentation of a specific implementation. */
 typedef struct psa_mac_operation_s psa_mac_operation_t;
@@ -661,6 +662,7 @@
  * \retval PSA_SUCCESS
  *         Success.
  * \retval PSA_ERROR_EMPTY_SLOT
+ * \retval PSA_ERROR_NOT_PERMITTED
  * \retval PSA_ERROR_INVALID_ARGUMENT
  *         \c key is not compatible with \c alg.
  * \retval PSA_ERROR_NOT_SUPPORTED