Harkrishan Vasudeva's interests are in functional analysis. This is their, together with Satish Shirali, fourth joint textbook, having previous published An Introduction to Mathematical Analysis (2014), Multivariable Analysis (2011) and Metric Spaces (2006). Vasudeva is the author of Elements of Hilbert Spaces and Operator Theory (2017) and co-author of An Introduction to Complex Analysis (2005).