mergeDbSources removes variables if field tags don't match

[Ali-Mahdipour]

When I am merging WOS and Scopus metadata the mergeDbSources appeantly removes columns with field tags that do not match in two dataframes. However I thought it would preserve them. This might be a problem related to convert2df function too. because I think it could have a standard set of field tags (like those listed here) and if some of them are not available show NA instead of removing those columns.