I'm pretty sure they are from this collection: https://en.wikipedia.org/wiki/Franz_Kafka:_The_Office_Writings https://en.wikipedia.org/wiki/Franz_Kafka:_The_Of

I'm pretty sure they are from this collection: https://en.wikipedia.org/wiki/Franz_Kafka:_The_Office_Writings https://en.wikipedia.org/wiki/Franz_Kafka:_The_Office_Writin... (Also I believe these letters are 'anonymous' not in the sense that their authorship is unknown, but in that they were published under the institutional name of the Insurance Institute where he was employed, not under his personal name.)