could not install pgAdmin4 on Debian Jessie

Hi, I've tried installing following the steps (among others) from
https://wiki.postgresql.org/wiki/Apt

And I've always got errors, the one I am reporting is:

# apt-get install postgresql-11 pgadmin4
Leyendo lista de paquetes... Hecho
Creando árbol de dependencias
Leyendo la información de estado... Hecho
Package pgadmin4 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

*E: Package 'pgadmin4' has no installation candidate *

I also tried with a virtualenv pgadmin4 and it wasn't possible.

I also hace another computer with a debian sid and I could install
postgresql and pgadmin4, buy not in jessie.

Also in jessie didn't work the pgadmin III. Always send messages about when
trying server connection.

--
Saludos cordiales, Reyna Melara.