Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Differential Equations
Hotmath provides 20 practice problems dealing with differential equations. Each of the practice problems include a step-by-step guide.
Wolfram Research
Wolfram Science World: Bernoulli, Jakob (1654 1705)
This site from ScienceWorld provides a brief but factual abstract of Bernoulli's math accomplishments. Links are provided throughout for additional information on related subjects.