Pliny attributes the invention of the triumph to "Father Liber" (identified with Dionysus): see Pliny, Historia Naturalis, 7.57 (ed. Bostock) at Perseus: Tufts.edu
uchicago.edu
penelope.uchicago.edu
Beard, 72-5. See also Diodorus, 4.5 at Thayer: Uchicago.edu
Beard, 16. For further elaboration on Pompey's 3rd triumph, see also Plutarch, Sertorius, 18, 2, at Thayer Uchicago.edu: Cicero, Man. 61: Pliny, Nat. 7, 95.
Suetonius, Lives, Claudius, 24.3: given for the conquest of Britain. Claudius was "granted" a triumph by the Senate and gave "triumphal regalia" to his prospective son-in-law, who was still "only a boy." Thayer: Uchicago.edu