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

According to the preface detailed in Chapter 0, a Sadguru takes two forms of service from devotees through books. The first method is when the Sadguru themselves create monumental spiritual works, like the Shri Dnyaneshwari or Shri Dasbodh. The second method involves the Sadguru having their biographies written by their devotees. In this latter case, the Sadguru accepts service through the dedicated study and devotional readings, or Parayans, of these biographies performed by both the author and the wider congregation of devotees, allowing all to achieve the purpose of their lives.