Appendix 2. Description of data mining procedure

Data mining has been performed on SCI Finder using the following procedure (after assessment and choice of keywords):

1. Search in "Research Topic"

2. Filtering of document type "Patents"

3. Retrieval of patents containing the chosen keyword with the option "As entered", always using the "Remove duplicates" option

4. Division of patents according to the registration year considering patents registered between 1998 to 2006 (SCI Finder records contain no data on citations in documents published before 1998);

5. Retrieval of cited reference for each group of patents (keyword-year)

6. Division of references according to their kind (patents, journals) and further division according to the year of publication