text1: How many vector equations did Heaviside and Gibbs reformilate Maxwell's 20 scalar equtions into?
text2: The origin of electric and magnetic fields would not be fully explained until 1864 when James Clerk Maxwell unified a number of earlier theories into a set of 20 scalar equations, which were later reformulated into 4 vector equations by Oliver Heaviside and Josiah Willard Gibbs.