Update bank account documentation.

doc/bank.md

@@ -10,6 +10,8 @@ Modules
 
 ### Bank Account
 
+    (import bank-account)
+
 This module creates a thin abstraction layer for bank accounts and
 transactions.
 
@@ -38,7 +40,7 @@ to change in the future.
 Adds (prepends) given ```transaction``` to the list of transactions of
 given bank ```account```.
 
-    (make-bank-transaction i d a c v m t)
+    (make-bank-transaction i d a c v m t A B s)
 
 * ```i``` - transaction id
 * ```d``` - date
@@ -47,6 +49,9 @@ given bank ```account```.
 * ```v``` - variable symbol
 * ```m``` - message
 * ```t``` - transaction type
+* ```A``` - account number
+* ```B``` - bank code
+* ```s``` - specific symbol
 
 Creates new bank transaction data structure. The underlying
 implementation is currently a record.
@@ -60,9 +65,20 @@ The following accessors are provided:
 * ```bank-transaction-varsym```
 * ```bank-transaction-message```
 * ```bank-transaction-type```
+* ```bank-transaction-account```
+* ```bank-transaction-specsym```
 
 More fields with accessors will be added as other modules will need
 them.
 
+    (bank-accounts-member? bas acc bc)
+
+* ```bas``` - list of known bank accounts
+* ```acc``` - account number (string)
+* ```bc``` - bank code (string)
+
+Returns true if given combination of ```acc```/```bc``` is in
+```bas```.
+
 ### Bank Fio