According to the provided text, what are the ways a Sadguru accepts service from devotees through books?

The preface detailed in Chapter 0 explains that a Sadguru takes two primary types of service from devotees through literary works. The first way is when the Sadguru creates great works themselves, such as the Shri Dnyaneshwari or Shri Dasbodh. The second method is when the Sadguru has their biographies written by their devotees. In this case, the Sadguru accepts service through the study and devotional readings, or Parayans, performed by both the writer and the wider congregation of devotees who engage with the biography.