vocabulary V2 {
  extern vocabulary V
  IsSource(Manuscript)
}

theory T2 : V2 {
  ! x : (~IsSource(x)) => ? y : CopiedBy(y,x) & VariantOf(y) = VariantOf(x).
}

term NbOfSources : V2 {
  #{ x : IsSource(x) }
}

procedure minSources(sample) {
  stdoptions.groundwithbounds=false
  stdoptions.symmetrybreaking='static'
  idpintern.setvocabulary(sample,V2)
  return minimize(T2, sample, NbOfSources)[1]
}

procedure findSources(samples) {
  local result = {}
  for _,sample in ipairs(samples) do
    local model = minSources(sample)
    if model then
      table.insert(result,{ getGrouping(model), getSources(model) })
    else
      table.insert(result,{ getGrouping(sample), {} })
    end
  end
  return result
} 

procedure getSources(model) {
  local sources = {}
  for tuple in tuples(model[V2::IsSource].ct) do
    local manuscript = tuple[1]
    table.insert(sources,manuscript)
  end
  return sources
}