I think this text and maths font, https://iopscience.iop.org/article/10.1088/2515-7639/abf0b5/pdf, see image below 
Do you know of an easy way to find them, so I can use them for future projects?
thank you
I think this text and maths font, https://iopscience.iop.org/article/10.1088/2515-7639/abf0b5/pdf, see image below 
Do you know of an easy way to find them, so I can use them for future projects?
thank you
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There is a complex relationship with PDF text and Fonts so to take the core of your question
∇· B = 4πgδ(r).Where CM is ComputerModern, around 47 styles in total but the majority of plain text in that page is MinionLT-Regular.
Command Line tools can show a page teardown, perhaps broken down to character level. Often not that useful as it shows subsets by object number.
But for single query, "Editor Apps" like "Acrobat Pro" or cheaper can quickly itemize characters. Generally viewers such as "Reader" can only list the styles.