Spahn setoid

References

• Erik Palmgren, Bishop’s set theory (2005) (pdf)

• Erik Palmgren, Constructivist and Structuralist Foundations: Bishop’s and Lawvere’s Theories of Sets (2009) (web)

The formalization of Bishop set is reviewed for instance in section 3 of

• Thierry Coquand, Arnaud Spiwack, Towards constructive homological algebra in type theory (pdf)