reference. Synthetic differential geometry [kock2006synthetic]

✍️source

@book{kock2006synthetic,
 title = {Synthetic differential geometry},
 author = {Kock, Anders},
 year = {2006},
 url = {https://users-math.au.dk/kock/sdg99.pdf},
 volume = {333},
 publisher = {Cambridge University Press}
}