RF: Chap2. suggest including associated metadata as part of solution to lesson 3.

[IanMulvany]

Could extend the following para

"With a DOI (identifying the exact time frame, sampling universe, data version, wave, aggregations,
state of knowledge, etc.), datasets are identified and quantitative research using confidential
microdata is reproducible. To make lives easier, DOIs also drastically facilitate the automatized
extraction of well-defined datasets from publications (comparable to largely standardized citations
of other publications, allowing easy retrieval of publication networks, etc.)." to include a reference too associated metadata.