Who are the individuals described as performing the highest Guru service by studying revered knowledge texts?

Chapter 0 describes individuals who perform the highest, incomparable, and salvation-granting Guru service by studying specific knowledge texts. These are people who choose to consider the authors of these great works, or even the revered texts themselves, as their personal Guru. The preface gives examples of such texts, including world-revered Marathi works like Shri Dnyaneshwari, Shri Nath Bhagavata, and Shri Dasbodh. Even though these are purely spiritual knowledge texts and not biographies, the devotees who study and recite them are engaging in a supreme form of Guru service.