The source of each series is provided in the field 'Fuente' of the corresponding
catalog. For example, for series 2665111:

knitr::kable(
  bde_catalog_search("2665111")[c(
    "Numero_secuencial",
    "Fuente"
  )]
)

|Numero_secuencial |Fuente   |
|:-----------------|:--------|
|2665111           |Eurostat |
