Anne Preller. A Language for Category Theory in which Natural Equivalence Implies Elementary Equivalence of Models. Math. Log. Q., 31(14-18):227-234, 1985. [doi]
@article{Preller85,
title = {A Language for Category Theory in which Natural Equivalence Implies Elementary Equivalence of Models},
author = {Anne Preller},
year = {1985},
doi = {10.1002/malq.19850311404},
url = {http://dx.doi.org/10.1002/malq.19850311404},
researchr = {https://researchr.org/publication/Preller85},
cites = {0},
citedby = {0},
journal = {Math. Log. Q.},
volume = {31},
number = {14-18},
pages = {227-234},
}