ad C. Sterckx, Dieux d’eau: Apollons celtes et gaulois, Bruxelles 1996. Argues that Lug and Óengus are respectively the only apollinean divinity and the only hermaic divinity in the Celtic pantheon, while Nechtan (who can also be named Manannán and Núada) is the water-god and primordial king with healing attributes.
ad G. Dumézil, Mythe et épopée III (1973), pp. 21-89; examines the aquatic and equine motifs occurring in the dindshenchas of Bóand, and discusses their relation to the Celtic and Scandinavian mythical figure of the water-horse.