note added

Author: ulf1

examples/profile-fractional-differentiation.ipynb

@@ -64,7 +64,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**Formula 1** (see Schoffer, 2003, p.50)\n",
+    "**Formula 1** (see Schoffer, 2003, p.50; The formula will **fail** for integral order $d\\in\\mathbb{N}$)\n",
     "\n",
     "$$\n",
     "(\\Delta^d x)_t = \\sum_{k=0}^\\infty \\frac{\\Gamma(k - d)}{\\Gamma(k + 1) \\, \\Gamma(-d)} \\, x_{t-k} \\\\\n",