Based on the provided text, who are the authors of Guru biographies that are considered less famous or accessible, and why?

The preface identifies a few Guru biographies that are not as widely known or available. According to chunk 10 of Chapter 0, the detailed and scholarly biography by Shri Samarth Sadguru Vasudevanand Saraswati Maharaj has not become as famous as the one by Shri Saraswati Gangadhar. Another biography, written by Shri Samarth Sadguru Dattatreya Maharaj of Balekundri, is mentioned in the same chunk as not yet having been printed or published, making it inaccessible to the public. Finally, while Shri Dasganu Maharaj's works are praised, chunk 11 of Chapter 0 notes they are 'very short,' which could contribute to their different status compared to more comprehensive works.