The addition law attached to a stratification of a hyperelliptic   Jacobian variety
  This article shows explicit relation between fractional expressions of Schottky-Klein type for hyperelliptic $\sigma$-functions and a product of differences of the algebraic coordinates on each stratum of natural stratification in a hyperelliptic Jacobian. 
Victor Z. Enolskii, Shigeki Matsutani, and Yoshihiro \^Onishi