An article in which Dion Bongaert's and Dirk Schoenmaker's research on green bonds is mentioned. The research proposed unbundling green bonds into a standard bond and a green certificate to take care of the green earmarking of bond revenues. In The Next Step in Green Bond Financing the academics wrote that while green bonds let issuers capture a clientele-induced yield discount, they fragmented bond issues, which was bad for liquidity and came at the expense of expected returns.