\usepackage {pstcol,pst-text}
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 \pstextpath
  {\pscurve(-4,-2)(-2,0)(0,-3)(2,-1)(3,-2)}
  {\color{blue}
  If you want to type
  $3 \int^x_y = \sum^{n=1}_{33}$
  and let it follow along a
  curving line  \ldots}
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