Riverside County and San Bernardino County to the north form this metro area. Like many such metro areas in the Southwest, it extends far into uninhabited desert areas, in this case east through the Mojave Desert to the Nevada/Arizona border. Larger than nine U.S. states, it is often referred to as the Inland Empire.
I agree with tchrist that the word doctor in doctor appointment is a noun (attributive noun I believe), although the definition of an attributive noun is a noun used as an adjective, so maybe it's just semantics at some point.
An appointment letter is the proof of this moment. An Official Letter Formats written by hierarchical superior or immediate superior to the selected person is called the appointment letter. There are several factors to be taken care of when writing one and an appointment letter template can make this task easy.