The text mentions two types of service a Sadguru takes through books. Can you explain these and how they relate to building a following for Sai Baba?

Chapter 0 outlines two ways a Sadguru receives service via books, which are central to building a community. The first is when the Guru creates a great work themselves, like Shri Dnyaneshwari. The second, more relevant to Sai Baba in this context, is when the Guru has his biographies written by his devotees. Service is then accepted through the study and Parayans performed by both the writer and the wider congregation of devotees. Annasaheb Dabholkar's Shri Sai Satcharita is presented as a prime example of this second form of service, creating a foundational text for the community to rally around.