It has been argued that two of the lines of this ode (17 and 34) are spurious. On this, and on the ode in general, see: Harrison, S. J. (1990). "The Praise Singer: Horace, Censorinus and Odes 4. 8". The Journal of Roman Studies, 80, 31–43.
For arguments for the identification see Minadeo, R. (1975–6). "Vergil in Horace's Odes 4.12". The Classical Journal, Vol. 71, No. 2, pp. 161–164; Porter, D. H. (1972). "Horace, Carmina, IV, 12". Latomus, T. 31, Fasc. 1, pp. 71–87; Belmont, D. E. (1980). "The Vergilius of Horace, Ode 4.12". Transactions of the American Philological Association (1974-2014), Vol. 110
(1980), pp. 1–20; for arguments against see Cairns, F. (2019). "'Vergilius' in Horace Odes 4.12", Phoenix, Vol. 73, No. 3/4, pp. 279–292. Fraenkel (Horace, 1957, p. 418) strongly rejected the identification, but Nisbet and Hubbard (1970, p. 40) think it is "probably" the poet.
Dettmer, H. M. R. (1976). The Structural Pattern of Horace's Odes. University of Michigan PhD. (See also: Dettmer, H. (1983). Horace: A Study in Structure, Hildesheim.)