This book was recommended to me by my awesome friend and fellow artist Daniel Colon. Apparently it does a good job tracing through the years artists' reconceptualization and reappropriation of previous artists' decisions in the genre of portraiture. Available on amazon.com. Wilton, Andrew. The Swagger Portrait: Grand Manner Portraiture in Britain from Van Dyck to Augustus John, 1630-1930. London: Tate Gallery Publications, 1992.