This article appears as pp. 33-64 of Sieghard Brandenburg, ed., Haydn, Mozart, and Beethoven— Studies in the Music of the Classical Period: Essays in Honour of Alan Tyson (Oxford: Clarendon Press, 1998). It is worth tracking it down. Webster compares the notation in the autograph against standardization in both the JHW and the Wiener Urtext editions. Here's just one of his illustrations (sans discussion):
