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.
Careers that require a doctoral degree are concentrated in healthcare, science and education. Individuals who enjoy intense study, research and academic environments should consider pursuing a doctoral program in their field of interest. The doctoral degree typically requires four to seven years to complete, but can lead to well-respected, high-paying careers. Psychologists Psychologists earn a PhD or Psy.D as a doctor of psychology. They evaluate and diagnose patient behavior and provide patient counseling and therapy to children and adults. They may specialize in treating emotional and mood disorders.