Let's define multi-attributes

Since #23 (closed) & #27 (closed) the code is now (basically) able to handle multi-attributes...means:

When the code finds multiple elements (via xpath) for base_classification, gnd_subject & work.id -> all of them are used.

So we could also define other attributes that could be treated like this!

@jose.calvotello If you like to...you could collect them here 😄