Documentation of gran tangential history

Hello everyone,

I have a question regarding the documentation of gran tangential history.
http://www.cfdem.com/media/DEM/docu/gran_tangential_history.html

In the documentation it says:
"The spring part of the tangential force (k_t) is a 'history' effect that accounts for the tangential displacement ('tangential overlap') between the particles for the duration of the time they are in contact. It is calculated by adding up the releative [sic!] tangential velocity at the contact point times the time-step size."

1. Does the second sentence refer to k_t or the 'tangential overlap'?
It seems to me like the second sentence should read:
The 'tangential overlap' is calculated by multiplying the relative tangential velocity at the contact point with the time-step size." [A]

2. Is the tangential overlap in LIGGGHTS corrected for rolling, as mentioned on page 527 in the paper of Di Renzi et al. [B]?

Could someone please advise?

Kind regards,
MiRa

[A] It would be nice, if the corresponding website would contain clean equations, such as the one for the Hertz-Mindlin model (http://www.cfdem.com/media/DEM/docu/gran_model_hertz.html)

[B] Di Renzo, Alberto; Di Maio, Francesco Paolo (2004): Comparison of contact-force models for the simulation of collisions in DEM-based granular flow codes. In: Chemical Engineering Science 59 (3), S. 525–541. DOI: 10.1016/j.ces.2003.09.037.