These statistics cover borrowing activity in debt capital markets. They capture debt instruments designed to be traded in financial markets, such as treasury bills, commercial paper, negotiable certificates of deposit, bonds, debentures and asset-backed securities, and distinguish between debt securities issued in international and domestic markets. BIS debt securities are harmonised with the recommendations of the Handbook on securities statistics, an internationally agreed framework for classifying debt securities issues "I find problems of optimal management of macroeconomic quantities—like public debt, inflation, or exchange rates—very interesting both from an everyday-life and a mathematical perspective," Ferrari says. "They lead to very challenging mathematical problems in which one needs to consider the interaction between several variables, including macroeconomic and financial quantities and multiple agents, such as government, central banks, and financial agents. I believe that there is still a lot to do in the mathematical analysis/modeling of such problems."