SHASHo density and score formulas in R/shasho_fit.R are adapted from
R/SHASHo.R in gamlss.dist version 6.1-1, distributed by CRAN under
GPL-2 | GPL-3, the same license alternatives as SVEMnet.

Upstream authors (as credited in man/SHASH.Rd): Robert (Bob) Rigby,
Mikis Stasinopoulos, and Fiona McElduff. The upstream DESCRIPTION names
Mikis Stasinopoulos as copyright holder. These credits apply to the
adapted formulas, not to the SVEMnet fitting engine or other package code.

Source: https://cran.r-project.org/src/contrib/gamlss.dist_6.1-1.tar.gz
Retrieved 2026-09-06; archive SHA-256:
d2db3a7658799c2ef212aa18cb75a3ecf4f73faf8c13dfdc3c14b21ae0129069
Original source comment: "This is the original SHASH distribution from
Jones and Pewse3y (2009) Biometrika. 1-20"; "see page 2 equation (2) of the
paper (divided by sigma for the density of the unstandardized variable)".

SVEMnet changes (2026-09-06): log-cosh evaluation for numerical stability,
analytic scores expressed on log-scale/log-tail parameter coordinates,
and a new, deterministic, multiple-start intercept-only optimizer using
stats::optim. No GAMLSS family or regression fitting engine is included.

The mathematical distribution is described in Jones, M. C. and Pewsey, A.
(2009), "Sinh-arcsinh distributions", Biometrika 96(4), 761-780.