13th International Conference on Graph Transformation
ICGT 2020
http://icgt2020.di.unipi.it
co-located with STAF 2020, June 22-26 Bergen, Norway

Fifth International Conference on
   Formal Structures for Computation and Deduction (FSCD 2020)
                 June 29 – July 5, 2020, Paris, France
                 http://fscd2020.org/

A Nice and Accurate Checker for the Mathematical Language Automath
http://www.cs.ru.nl/~freek/aut/aut-4.1-manual.pdf
Considering it's a proof checker, one should probably expect it to be accurate, or so I guess :D

Multicore OCaml: January 2020 update - Community - OCaml
https://discuss.ocaml.org/t/multicore-ocaml-january-2020-update/5090

This text develops a comprehensive theory of programming languages based on type systems and structural operational semantics. Language concepts are precisely defined by their static and dynamic semantics, presenting the essential tools both intuitively and rigorously while relying on only elementary mathematics. These tools are used to analyze and prove properties of languages and provide the framework for combining and comparing language features. The broad range of concepts includes fundamental data types such as sums and products, polymorphic and abstract types, dynamic typing, dynamic dispatch, subtyping and refinement types, symbols and dynamic classification, parallelism and cost semantics, and concurrency and distribution. The methods are directly applicable to language implementation, to the development of logics for reasoning about programs, and to the formal verification language properties such as type safety.

Incomplete and Utter Introduction to Modal Logic, Pt. 1/2
https://serokell.io/blog/incomplete-and-utter-introduction-to-modal-logic
https://serokell.io/blog/rapid-introduction-to-modal-logic-2
[Thanks to GNU/Garak]

ZZ, a formally verifiable dialect of C
https://github.com/aep/zz
[Thanks to swarnim]

Petri Nets are Monoids
https://core.ac.uk/download/pdf/82342688.pdf
[Thanks to Elias]