Foster-D'Angelo
Multiple realities
(covers information from several alternate timelines)
Foster-D'Angelo was a star system in the Alpha or Beta Quadrant.
In 2367, Foster-D'Angelo's position was labeled on a tactical situation monitor in Captain Benjamin Maxwell's ready room on the USS Phoenix. (TNG: "The Wounded", okudagram)
In 2366, in an alternate timeline, during the Federation-Klingon War, Foster-D'Angelo's position was labeled on a tactical situation monitor on the bridge and in the ready room of the USS Enterprise-D. (TNG: "Yesterday's Enterprise", okudagram)
This star system was only mentioned in writing.
It can't be deduced from the star chart in which quadrant Foster-D'Angelo was located as there were planets and star systems from both quadrants spread throughout the chart.
Foster-D'Angelo was named after swing gang members Don Foster, Jr. and Dick D'Angelo.