As an addition to your transcription, here is the last letter transcribed:

    to John Backus
    91 Saint Germain Avenue
    SAN FRANCISCO, California 94114
    U.S.A.
                          12th July 1979
    
    Dear John,
       My schedule is very tight, and I am afraid that I
    must disappoint John Williams; Monday 20 or Tuesday 21
    August seem the only two slots that are really available.
      I shall arrive in the USA on Sunday 29th July, and
    had already committed myself for the week of Monday
    30 July to Burroughs in Mission Viejo. My wife and
    the two youngest children will join me for the first
    three weeks of the trip, and the week of 6th August
    was planned as "the real holiday." Since then Bill
    McKeenan has twisted my arm: the programming
    course to be given that week was so heavily over-
    booked that he asked me to give a second course,
    in parallel to David's. Under those circumstances
    I would like to avoid further commitments in
    the week starting on Monday 13: it is their last
    week in the USA, and I have then been working
    almost all the time!
      Immediately after WG2.3 I shall go to Austin,
    Texas (Burroughs and University), and then home!
    If I have a completely free choice, I think I
    would prefer Monday 20 slightly over Tuesday 21.
    
    New title and abstract:
    
    Title: Termination Detection for Diffusing Computations
    
    Abstract: The activity of a finite computation may
    propagate over a network of machines, when machines
    may delegate (repeatedly) subtasks to their
    neighbours; when such a computation is fired
    from a single machine, we call it "a diffusing
    computation." We present a signalling scheme
    --to be superimposed on the diffusing computation--
    enabling the machine that fired it to detect its
    termination. Our signalling scheme is perfectly
    general in the sense that, independently of the
    topology of the network, it is applicable to
    any diffusing computation. (End of abstract.)
    
      Please give my regards to John Williams and tell
    him how sorry I am that I shall miss him. I
    am not familiar with distance and transport facilities
    between Santa Cruz and San Jose. If it is better
    when I come to San Jose the day before that
    is fine with me; may I leave the logistics to
    you? (Wife and children leave on Friday 17th of August.)
    With my greetings and best wishes,
                     yours ever
                          _Edsger_