The continuation of the Schwarzschild metric across the event horizon is almost always (in textbooks) carried out using the Kruskal-Szekeres coordinates, in terms of which the areal radius r is defined only implicitly. We argue that from a pedagogical point of view, usi... View more
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 The Gautreau-Hoffmann coordinates are very similar to the coordinates of Sec. III. They also constitute a oneparameter family of coordinate systems, and their parameter Ri is related to our p by Ri = 2M p/(p − 1). The difference lies with the fact that while their Ri is not meant to be negative, our p is restricted to the interval 0 < p ≤ 1. These are mutually exclusive statements. But the point remains that formally, the coordinates of Sec. III are identical to the Gautreau-Hoffmann coordinates for Ri < 0. Note that for Ri > 0 (the case considered by Gautreau and Hoffmann in Ref. ), the surfaces of constant time extend only up to r = Ri; they do not reach infinity.
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