James R. Harrison, “The Brothers as the ‘Glory of Christ’ (2 Cor 8:23): Paul’s doxa Terminology in its Ancient Benefaction Context,” Novum Testamentum 52 (2010) 156–88.
Stephen Joubert, “Religious Reciprocity in 2 Corinthians 9:6–15: Generosity and Gratitude as Legitimate Responses to the χάρις τοῦ Θεοῦ,” Neotestamentica 33 (1999) 79–90.
Jan Lambrecht, “Paul’s Boasting about the Corinthians: A Study of 2 Cor 8:24–9:5,” Novum Testamentum 40 (1998) 352–68.
Stewardship: Able To: All You’re Capable Of 2 Corinthians 8:3-5, at preaching.com