Changju Lee and  Seungmo Ku and  Sondo Kim and  Woojin Chang,  Detecting Financial Bubbles Using Gap between Common Stocks and Preferred Stocks.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2017, vol. 122(2). 301 - 307
    [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/10006194.