Implemement an OpenRefine reconciliation service API. This example uses CrossRef's API to convert citation strings into DOIs.
Once data is reconciled you can creat a column of DOIs by clicking on the header of the column containing the citation strings and choose Edit column → Add column based on this column... and a dialog box will be displayed. In the box labelled Expression enter cell.recon.match.id and give the column a name (e.g., "DOI"). You will now have a column of DOIs for the citation strings.