  Norden E. Huang, Fangli Qiao and Ka Kit Tung presented a data-driven model
for the COVID-19 epidemic in which the relevant functions depend on a set of
seven parameters obtained from a statistical analysis of the available data.
These parameters are not independent, they are linked through a set of
relations the authors call Main Results which are validated by a statistical
analysis of the data. The parameters in questions and the relations between
them are not always explicitated by the authors. By given them here their
(simple) mathematical formulations all the relevant functions describing the
dynamic can be explicitely written down. All the explicit formulas follow from
the fact that the log of the number of infected, is a quadratic function of
time. The formulas presented here are not themselves approximations - but the
parameters they involve are of course statistical quantities derived from the
data. These formulas could maybe be of some use either to validate the data,
the model itself, to update the model or to find approximations to the relevant
quantities.
