Seng-Tiong Ho and Allen Taflove were professors of engineering at Northwestern University, where Yingyan Huang and Shi-Hui Chang were graduate students.

Within a year Ho had completed the mathematical derivations of his model, notes and equations of which were hand-written in about sixty-nine pages.

They alleged copyright infringement and state law claims of false designation of origin, unfair competition, conversion, fraud and misappropriation of trade secrets involving six documents published by the defendants.

Their main argument was that the defendants had copied an "expression of complicated physical phenomenon" consisting of the model, derivation of equations and two figures and therefore infringed on their copyrights.

[2] The defendants' counter argument states that the model and equations are ineligible for copyright protections under the merger doctrine because there are so few different ways to express a mathematical concept.

The district court granted summary judgement in favor of the defendants, asserting that the model was indeed an idea and therefore not eligible for copyright protection.

The defendants argued that under Illinois state law their claim for conversion is not valid because it was not physical property but the plaintiffs' research ideas.

[2] The plaintiffs alleged that intangible items in a tangible medium were proper subjects of a conversion claim and because Chang & Taflove held physical copies of Ho's notebooks and Huang's thesis only reaffirmed their argument.

1990) which states that "the possession of copies of documents-as opposed to the documents themselves-does not amount to an interference with the owner's property sufficient to constitute conversion.

In regard to copyright, the court of appeals stated that the plaintiffs failed to show alternative ways in which the model could be expressed.