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 |