Can you provide a summary of the various authors of Guru biographies mentioned in the preface and the key details about their works?

The preface in Chapter 0 discusses several authors of Guru biographies. Shri Dasganu Maharaj is credited with two short but graceful biographies of Sai Baba. Shri Saraswati Gangadhar is noted as the author of the famous 'Brihad Guru Charitra' and is a descendant of Shri Sayandev. Another author, Shri Samarth Sadguru Tembhe Swami, also known as Vasudevanand Saraswati Maharaj, wrote a detailed and scholarly biography that is considered less famous and is in a separate category because he wrote it himself. The text also mentions an unpublished Guru biography by Shri Samarth Sadguru Dattatreya Maharaj of Balekundri. Finally, Annasaheb Dabholkar is mentioned in contrast to Dasganu Maharaj for his different thematic focus.