Improved BFT embedding having chain-structure
  We newly revisit the gauge non-invariant chiral Schwinger model with a=1 in view of the chain structure. As a result, we show that the Dirac brackets can be easily read off from the exact symplectic algebra of second-class constraints. Furthermore, by using an improved BFT embedding preserving the chain structure, we obtain the desired gauge invariant action including a new type of Wess-Zumino term. 
Yong-Wan Kim, Ee Chang-Young, Seung-Kook Kim, Young-Jai Park