What are the two primary ways a Sadguru accepts service from devotees through books?

According to the source text, a Sadguru accepts service through books in two main ways. The first is when the Guru creates great works themselves, with examples given like Shri Dnyaneshwari or Shri Dasbodh. The second method, as explained in Chapter 0, is by having their biographies written by their devotees. In this case, the Guru accepts service in the form of study and Parayans (devotional readings) from both the writer and the entire congregation of devotees who engage with the text. This allows many to participate in the service.