Authors that need an invitation letter to attend SOCO 2019 please, send and email to: SOCO 2019 Secretariat (fmaralv@upo.es) giving all the details related to your paper: Id, title, authors, affiliation and also including the proper information about where to send it.
Additionally, please tell us if you need only a scanned version of the letter or if you need the original letter to be sent to you via mail.