Reproducing subgroups of $Sp(2,\mathbb{R})$. Part I: algebraic   classification
  We classify the connected Lie subgroups of the symplectic group $Sp(2,\mathbb{R})$ whose elements are matrices in block lower triangular form. The classification is up to conjugation within $Sp(2,\mathbb{R})$. Their study is motivated by the need of a unified approach to continuous 2D signal analyses, as those provided by wavelets and shearlets. 
Giovanni S. Alberti, Luca Balletti, Filippo De Mari, Ernesto De Vito
math.GR math.FA