Using Sidereal Time and Geocentric Coordinates

My recent interest in calculating LMST (Local Mean Sidereal Time) came
about from a paper some 30 years old in which the author produce "The
rectangular geocentric systems of coordinates is given by:

X = (R+h)*cos(phi')*cos(LMST)
Y = (R+h)*cos(phi')*sin(LMST)
Z = (R+h)*cos(phi')
where phi' is the geocentric latitude.

I have not found these equations on the web, and am beginning to think
they have been replaced over the decades. Comments?