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

According to the preface detailed in Chapter 0, a Sadguru accepts service from devotees through books in two distinct ways. The first is when the Sadguru creates great spiritual works themselves, with Shri Dnyaneshwari and Shri Dasbodh cited as examples. 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 Parayans (devotional readings) performed by both the writer and the wider congregation of devotees. This allows the Guru's message and life to be disseminated widely, benefiting all who engage with the text.