  A rule of thumb derivation of the Dirac-Born-Infeld action for D-branes is
studied \`a la Fradkin and Tseytlin, by simply integrating out of the
superstring coordinates in a narrow strip attached to the D-branes. In case of
superstrings, the coupling of Ramond-Ramond fields as well as the
Dirac-Born-Infeld type coupling of the Neveu Schwarz-Neveu Schwarz fields come
out in this way.
