The website LeicaPhotographyArchive started uploading online scans of old Leica Photography magazines that can be used as a reference for anything related to Leica cameras and Leitz company. All scanned magazines can be accessed here. You can add the scans to your Google drive and then download them (total of 876MB so far). This is an ongoing project, so check the website in the future for new additions to the archive. Here is a screenshot of the currently available issues: