Thus by 1803 there were two known rare earth elements, yttrium and cerium, although it took another 30 years for researchers to determine that other elements were contained in the two ores ceria and yttria (the similarity of the rare earth metals' chemical properties made their separation difficult).
For instance, students who pursue a Ph.D. in psychology usually take from five to seven years depending upon required coursework as well as internship and supervised residency requirements.
How long it takes to earn a doctorate in psychology depends on a number of factors including the field of psychology you pursue, your specialty, and even the school where you eventually earn your degree. Typically, it takes anywhere from five to seven years to earn a doctorate in psychology. Some specialties, such as licensed clinical psychology, also require the completion of a one to two year supervised residency program following the completion of a doctorate degree.