According to the provided text, in what two ways does a Sadguru accept service from devotees through books?

The source material in Chapter 0 explains that a Sadguru accepts service from devotees through literary works in two distinct manners. The first is when the Sadguru authors great spiritual works themselves, with examples given such as the Shri Dnyaneshwari or Shri Dasbodh. The second method involves the Sadguru inspiring devotees to write their biographies. The Sadguru then accepts this service in the form of study and Parayans (devotional readings) performed by both the writer and the wider congregation of devotees, allowing many to achieve the purpose of their lives through this engagement.