Clarifications about a formula

I reading the TRIGRS manual I fond this:

Comparison of Computed Results with Published Analyses

We tested TRIGRS against Iverson’s (2000) examples from the Minor Creek landslide and from an experiment at the USGS debris-flow flume and were able to reproduce his results for pore pressure and factor of safety profiles. Thus, we were able to verify that the computer code accurately implements Iverson’s (2000) formulas for pore pressure and factor of safety. After publishing the original version of TRIGRS, students of Ricardo Rigon (University of Trento, Trento, Italy) pointed out an error in the coordinate transformation in Iverson’s (2000) original paper. Correction of that simple error causes our numerical results to differ somewhat from Iverson’s (2000) published values, though preserving their basic form. Folders named

25“MinorCreek” and “flume” contain files with necessary data to reproduce these results. By varying elapsed time, t , in the initialization file, the user can compute pressure head and factor of safety profiles like those of figures 7, 8, 10, and 11 of Iverson (2000). Note that the computed profiles conform to the limit imposed by equation 3. We have also verified that the new version of TRIGRS described in this report reproduces the published results of Srivastava and Yeh (1991). Data in the folder “sy91” produce profiles that allow the user to reproduce the curves plotted in figure 3 of Srivastava and Yeh (1991).

A part the misspelling of my name (two "r"s, not one like in Spanish), I need to precise that the error was discovered by Emanuele Cordano, a.k.a. the authors of at least  couple of papers with me, and some R packages useful for hydrologists.  His papers, maybe difficult to read, and so far not kissed by the goddess of citations,  remain among my own favorite. 

References

[ J28] - Cordano E. R. Rigon, A perturbative view on the subsurface water pressure response at hillslope scale, Water Resour. Res., Vol. 44, No. 5, W05407- W05407, doi:10.1029/2006WR005740, 2008

[J38] - Cordano, E., and R. Rigon (2013), A mass-conservative method for the integration of the two-dimensional groundwater (Boussinesq) equation, Water Resour. Res., 49, doi:10.1002/wrcr.20072.

Boussinesq code is available on Github.

R- Software

RMWAGEN, a weather generator, a package that contains functions for spatial multi-site stochastic generation of daily timeseries of temperature and precipitation. A presentation can be found here.

Soilwater, A package for plotting soil water retention curves and hydraulic conductivity written by Emanuele Cordano, Fabio Zottele and Daniele Andreis.