abstract Examples = {

cat
  Ex ;
fun 
  ex1, ex2, ex4, ex8, ex13, ex19, ex20, ex23,
  ex3, ex5, ex6, ex7, ex10, ex12, ex14, ex15, ex16, ex24, ex25, ex26, ex27,
  ex9,
  ex11, ex17, ex18, ex21, ex22 : Ex ;
}