Stephen Carlson here noted a PDF of an article by H.J. de Jonge on the Comma Johanneum here. This made me aware that through Leiden University's open access catalogue a significant number of publications relevant to TC are available freely online.
Take the following articles by de Jonge:
'Erasmus und die Glossa Ordinaria zum Neuen Testament'
'Erasmus' New Testament Translation Method'
In fact there are no fewer than 119 titles by de Jonge available here. But I also saw one piece by J. Delobel and if one were to search the facility I'm sure that more relevant material would emerge.