Efficient information flow in technical communication depends upon accurate audience analysis. The presentation of information must be adjusted relative to the knowledge and interests of the writer's audience. Problems arise when the relative differences in audiences are slight, but nonetheless important. Albert Einstein's writing can be used as an example of skillful adaptation of material for audiences with subtle differences. A prime example is his special theory of relativity, which he published in three versions for technical, semitechnical, and nontechnical audiences. Students, teachers, and technical writers can learn much from the way Einstein uses tone, personal address, varying levels of diction, definitions, and concrete examples of each of the three expositions of his special theory of relativity.