That should have been "Sin puertas visibles," not "Puertas invisibles." I've corrected yesterday's post after someone kindly called the mistake to my attention.

I just threw away 300 messages in my deleted message file in my email, without bothering to check to see whether I was saving them for any particular reason. Now, return library books, grade papers: end of semester ritual.

The system apparently lost most of Friday's email. If I failed to answer any mail you sent me that day that is probably the reason.