The postcard states:

Dear Professor Dijkstra,

this is to inform you that I have just read and enjoyed your EWD1000. Since prof. W. Fejen's [sic] visit at our Department I have been intensively interested in ideas of "Dijkstra's school" and for two years I have (sometimes unregular) access to your writings. Thank you very much for writing them.

Yours sincerely, Luboi Brim.