And those aren't the only references to Demy's films: as Ismaël and Erwann are walking along the street two sailors are at the back of them, which is an allusion to the group of sailors in both Les Demoiselles de Rochefort and Lola; the three sisters in Chansons bear the surname Pommeraye, a reference to the Passage Pommeraye in Demy's Nantes, which features in Lola; Catherine Deneuve plays Geneviève in Parapluies, where they eat the galette des rois and Geneviève is crowned queen, whereas in Chansons it's Jeanne Pommeraye (Chiara Mastroianni), who is Deneuve's real daughter, who is crowned; etc.
Of course, Demy is not the only director associated with the Nouvelle Vague whom Honoré pays homage to: the ménage à trois of Ismaël, Julie and Alice refers, for instance, principally to Truffaut's Jules et Jim and (to a lesser extent) Les deux anglaises et le continent – both based on two autobiographical novels of the same name by Henri-Pierre Roché – but I'll come to literary references proper in the next paragraph;* on the telephone, Julie tells Ismaël: 'je pense à quelque chose tout à coup...tu m'emmerdes' ('I've suddenly thought of something...you piss me off'), which is exactly the same line Angela tells Émile in Godard's Une femme est une femme; etc.
As for literary references, they are all over the film: Ismaël, Julie and Alice read Alison Louise Kennedy, James Salter and Adam Thirlwell in (the same) bed (and inevitably this reminds us of Jean-Paul Léaud reading in bed in Truffaut); if Erwann's books by Edmund White, Hervé Guilbert and Dennis Cooper are indicative of a homosexual content, Ismaël's 'Salinger quand même' is a tacit note that not all Erwann's book collection has the same subject; etc.
This is an intelligent, humorous, delightful feast of a film.
*The famous ménage à trois in Jean Eustache's La Maman et la putain could of course also of note.