Wilfried Sieg. Only two letters: The correspondence between Herbrand and Gödel. Bulletin of Symbolic Logic, 11(2):172-184, 2005. [doi]
@article{Sieg05:0, title = {Only two letters: The correspondence between Herbrand and Gödel}, author = {Wilfried Sieg}, year = {2005}, url = {http://www.math.ucla.edu/~asl/bsl/1102/1102-005.ps}, researchr = {https://researchr.org/publication/Sieg05%3A0}, cites = {0}, citedby = {0}, journal = {Bulletin of Symbolic Logic}, volume = {11}, number = {2}, pages = {172-184}, }