title: How to structure scientific references into groups using R?
body: <p>Lets imagine the following two references:</p>
  <pre><code>ref1 &lt;- &quot;Smith, A. L., Reganold, J. P., Jones, M. S., Orpet, R. J., Taylor, J. M., Thurman, J. H., Cornell, K. A., Olsson, R. L., Ge, Y., Kennedy, C. M., &amp; Crowder, D. W. (2020). Landscape context affects the sustainability of organic farming systems. Proceedings of the National Academy of Sciences, 117(6), 2870–2878. https://doi.org/10.1073/pnas.1906909117&quot;
  
  ref2 &lt;- &quot;Muller, A., Schader, C., El-Hage Scialabba, N. et al. Strategies for feeding the world more sustainably with organic agriculture. Nat Commun 8, 1290 (2017). doi.org/10.1038/s41467-017-01410-w&quot;
  </code></pre>
  <p>And I would like to group this data into (for example)</p>
  <pre><code>data.frame(first_author = c(&quot;Smith, A. L.&quot;,&quot;Reganold, J. P.&quot;), 
            second_author = c(&quot;Muller, A.&quot;,&quot;Schader, C.&quot;),
            year = c(&quot;2020&quot;,&quot;2017&quot;),
            title = c(&quot;Landscape context affects the sustainability of organic farming systems&quot;,&quot;Strategies for feeding the world more sustainably with organic agriculture&quot;), 
            journal = c(&quot;Proceedings of the National Academy of Sciences&quot;,&quot;Nat Commun&quot;),
            volume.issue = c(&quot;117(6)&quot;,&quot;8(1290)&quot;),
            pages = c(&quot;2870–2878&quot;,NA),
            doi = c(&quot;https://doi.org/10.1073/pnas.1906909117&quot;,&quot;doi.org/10.1038/s41467-017-01410-w&quot;))
  
  </code></pre>