Question: Please suggest books/references on ARDL model and ARDL bounds test approach to study.

Answer: 
A classical textbook on cointegration in the ADL/ECM framework is [Co-integration, Error Correction, and the Econometric Analysis of Non-Stationary Data](https://global.oup.com/academic/product/co-integration-error-correction-and-the-econometric-analysis-of-non-stationary-data-9780198288107?q=cointegration&lang=en&cc=fi) by Anindya Banerjee, Juan J. Dolado, John W. Galbraith, and David Hendry. Another good text is [Time-Series-Based Econometrics: Unit Roots and Co-integrations](https://global.oup.com/academic/product/time-series-based-econometrics-9780198773535?cc=fi&lang=en&) by Michio Hatanaka.
Btw, there is now a user-written Gretl package for running a bootstrap version of both the PSS and BDM bounds test on cointegration. For an example see [here](https://sites.google.com/site/arturtarassow/it-s-not-really-ablog-but-rather-a-note-to-myself/replicating-eviews-blog-entry-on-ardl-based-cointegration-tests).