Beethoven's Immortal Beloved: Marek's Research
Bernard Rose's 1994 movie "Immortal Beloved" sparked again my interest in discovering the identity of the woman to whom Beethoven wrote his passionate letter; she has had musical detectives in hot pursuit for well-nigh two centuries. George Marek conscientiously reviews the list of possible candidates in his Beethoven: Biography of a Genius and, after painstaking research, proposes Dorothea Baroness von Ertmann.
Ibes, Willem (Wim), "Beethoven's Immortal Beloved: Marek's Research" (2002). Music Lectures. 5.