..the problem of building a citation graph by reliably extracting references from full-­texts and detecting their true targets. This is a fairly complicated problem due to the variability of citation styles and inconsistent usage of Document Object Identifiers (DOIs). As a solution we have tested a number of citation extraction tools and also adopted the CrossRef API 13 for detecting DOIs based on citation references. While this helps us to create edges in the citation graph with fairly high accuracy, it has been a bottleneck in our processing queue, because we currently need to issue more DOI resolution requests per unit of time than the API could handle. We raised this issue with CrossRef and they have been very kind in offering help and we believe that a solution is on the way.