Kramers-Kronig resources

So in my work I've had the pleasure of utilizing the Kramers-Kronig relations numerically to help solve certain problems. I understand the basics of how they are applied and their relationship to response functions. I'm looking for a deeper understanding in the general sense, both in the mathematics and some of the fundamental physics behind their application.

If anyone is aware of any resources (review articles, textbooks, pdf's etc.) that could aid me in my plight I would be very grateful.

Feel free to give materials that review this from either a mathematics, physics, or applied spectroscopy vantage point. I don't really care. I'm just very interested and want to further my knowledge in this seemingly rich topic.

Thanks in advance to anyone who responds.