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.
1 How long does it take to get degrees in psychology? 2  Most bachelor's degree programs are designed as 4-year programs. 3  Most master's degree programs are designed to take 2-1/2 years. 4  Most doctoral degree programs are designed to take about 5 years (if you do not already have your master's degree).