The law of corresponding states was first suggested and formulated by van der Waals in 1880. This showed that the van der Waals equation of state can be expressed as a simple function of the critical pressure, critical volume and critical temperature. This general form is applicable to all substances. The compound-specific constants a and b in the original equation are replaced by universal (compound-independent) quantities. It was this law that served as a guide during experiments which ultimately led to the liquefaction of hydrogen by James Dewar in 1898 and of helium by Heike Kamerlingh Onnes in 1908. Lorentz ether theory has its roots in Hendrik Lorentz's "theory of electrons", which was the final point in the development of the classical aether theories at the end of the 19th and at the beginning of the 20th century. Lorentz's initial theory created in 1892 and 1895 was based on a completely motionless aether. Many aspects of Lorentz's theory were incorporated into special relativity with the works of Albert Einstein and Hermann Minkowski. In 1892, Hendrik Lorentz derived the modern form of the formula for the electromagnetic force which includes the contributions to the total force from both the electric and the magnetic fields. In many textbook treatments of classical electromagnetism, the Lorentz force law is used as the "definition" of the electric and magnetic fields E and B. To be specific, the Lorentz force is understood to be the following empirical statement:  In the physics of electromagnetism, the Abraham–Lorentz force (also "Lorentz-Abraham force") is the recoil force on an accelerating charged particle caused by the particle emitting electromagnetic radiation. It is also called the "radiation reaction force" or the "self force". In physics, the Lorentz transformation (or Lorentz transformations) is named after the Dutch physicist Hendrik Lorentz. It was the result of attempts by Lorentz and others to explain how the speed of light was observed to be independent of the reference frame, and to understand the symmetries of the laws of electromagnetism. The Lorentz transformation is in accordance with special relativity, but was derived before special relativity. Early approximations of the transformation were published by Lorentz in 1895. In 1905, Poincaré was the first to recognize that the transformation has the properties of a mathematical group, and named it after Lorentz.