SQL Server 2008 Select all columns of a table + a column from the same table based on a column value

I have a table VERSION with composite keys docId, verId:

docId   verId   apprvDt      old_verId   
------  ------  -----------  ----------
A       3       03/20/2017   2
A       2       03/18/2017   1
A       1       03/16/2017   null
B       1       03/18/2017   null
C       2       03/20/2017   1
C       1       03/16/2017   null

Say I select docId=A, verId=3, query should retu

docId   verId   apprvDt      old_verId   old_apprvDt
------  ------  -----------  ----------  ------------
A       3       03/20/2017   2           03/18/2017

I tried:

select a.docId, a.verId, a.apprvDt, a.old_id, b.old_apprvDt  
from VERSION as a left join 
   (select x.docId, x.verId, x.apprvDt from REVISN as x 
    where x.docId = 'A' and x.verId = a.old_verId) as b
on b.docId = a.docId and b.verId = a.old_verId

but I am getting a multi-part binding error.