What exactly are the stages of sravana, manah and nidhidhyasan (hearing, contemplation and assimilation)?

From Ramabhadrapriya Pr:

the process of knowledge is mentioned as stages of sravana, manah and nidhidhyasan ( hearing, contemplation and assimilation) . What are these stages, do you have any material on this subject, are there any books or previous acharyas books where this is discussed.