Modelltheorie und Logik. H.-D. Ebbinghaus (1974/1975) Jahresbericht der Deutschen Mathematiker-Vereinigung
More on injectivity in locally presentable categories. Rosicky, J., Adamek, J., Borceux, F. (2002) Theory and Applications of Categories [electronic only]
Mostowski's collapsing function and the closed unbounded filter K. Barwise (1974) Fundamenta Mathematicae