Andrew W. Swan. CZF does not have the existence property. Annals of Pure and Applied Logic, 165(5):1115-1147, 2014. [doi]
@article{Swan14,
title = {CZF does not have the existence property},
author = {Andrew W. Swan},
year = {2014},
doi = {10.1016/j.apal.2014.01.004},
url = {http://dx.doi.org/10.1016/j.apal.2014.01.004},
researchr = {https://researchr.org/publication/Swan14},
cites = {0},
citedby = {0},
journal = {Annals of Pure and Applied Logic},
volume = {165},
number = {5},
pages = {1115-1147},
}