@article{Geo:73b,
  journal = {Stud. Cerc. Mat.},
  volume = {25},
  title = {Injective and projective objects in various concrete categories},
  author = {Georgescu, George},
  year = {1973},
  fjournal = {Studii \c si Cercet\u ari Matematice},
  pages = {505--532},
}