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.
Yes but to get a doctorate in engineering you need to do a Ph.D which usually takes around 4 years after college (the same as medical school), the difference is that a recent medical school graduate cannot safely treat patients on his/her own. The reason is that the consequences of that new doctor missing something is literally life or death.