Penrose diagrams are often discussed in brief within existing literature, with common references to Minkowski and Schwarzschild metrics. Penrose's book "Cycles of Time" is noted for its accessible explanations and numerous examples, though it lacks mathematical rigor. For a more detailed mathematical approach, Hawking and Ellis, as well as Winitzki's online resource, are recommended, with Winitzki providing unique insights into the mapping properties in the Minkowski case. There is a consensus that while Penrose offers a synoptic view, a comprehensive mathematical treatment of the fundamental principles is still lacking in the literature. Overall, the discussion highlights the need for clearer, detailed mathematical descriptions of Penrose diagrams beyond the special cases typically presented.