Nigel Foster. EU Law Directions 6 ed. 2018. p. 60
2.5.1 Composition and organisation
The CoJ presently consists of 28 judges, one for each member state (as from 1 July 2013) and 11 Advocates-General (AGs) (as from 7 October 2015) (Article 252 TFEU), nominated and appointed by unanimous agreement by the governments of the member states for a renewable period of six years.
The Court can sit as a full court with a quorum of 17 judges, a Grand Chamber of 15 judges with a quorum of 11 to hear cases involving either member states or Union institutions, or in chambers of three or five judges and of which there are 10 in total.
Both text-books imply that the Grand Chamber requires 15 judges. See Foster – isn't the "quorum" 15? How can there be a "quorum of 11"?
See Alina – If you have a chamber of 5 judges, how can quorum be 3? If quorum is 3, then you have a chamber of 3, not 5!