Based on the total scholarly article output of Norway, we investigated the coverage and degree of openness according to the following three bibliographic services: (1) Google Scholar, (2) oaDOI by Impact Story, and (3) 1findr by 1science. According to Google Scholar, we found that more than 70% of all Norwegian articles are openly available. However, the degrees of openness are profoundly lower according to oaDOI and 1findr at 31% and 52%, respectively. Varying degrees of openness are mainly

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... sed by different interpretations of openness, with oaDOI being the most restrictive. Furthermore, open shares vary considerably by discipline, with the medicine and health sciences at the upper end and the humanities at the lower end. We also determined the citation frequencies using cited-by values in Google Scholar and applying year and subject normalization. We found a significant citation advantage for open articles. However, this was not the case for all types of openness. In fact, the category of open access journals was by far the lowest cited, indicating that young journals with a declared open access policy still lack recognition.