Answer to Question 55: Are there pictorial examples that distinguish   covariant and contravariant vectors?
  We present pictorial means of distinguishing contravariant vectors (or simply vectors) from covariant vectors (or linear forms). When one depicts vector as the directed segment, then the pictorial image of a linear form is a family of equidistant parallel planes with an arrow joining the neighbouring planes and showing the direction of increase of the form. First of these planes is the linear subspace of dimension two on which the linear form gives value zero. Several examples of physical quantities are given which are naturally vectors, and others which are naturally linear forms. 
Bernard Jancewicz (University of Wroclaw)