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.
Step 6: Complete degree requirements. Most doctoral level psychologists spend at least four years completing their graduate education. They will take practicum courses that begin to give them experience in the field -- and, in some cases, references. Some students choose to join APA divisions related to their practice area.