diff --git a/1_Basics.ipynb b/1_Basics.ipynb
index 22fc794797926bcd5bab59c03de4a5946df401f2..7f816cecfd0d785cda2d2f8c4fe5c084667c02a8 100644
--- a/1_Basics.ipynb
+++ b/1_Basics.ipynb
@@ -596,18 +596,112 @@
     "Use this formula to compute an estimate of π. It should use a while loop ot compute terms of the summation untile the last term is smaller than 1e-15. Afterwards, you can check the result by comparing it to π (to get π in Julia, write \\pi and then press TAB)."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "d4a870c3-7679-4775-94ce-4e7266a2bebe",
+   "metadata": {},
+   "source": [
+    "## Functions"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "682a3feb-0b82-479d-9803-3011a1e6e521",
+   "metadata": {},
+   "source": [
+    "We have already seen one example of a function call:"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "cd1a716d-ddaf-4167-a83f-129dc3163ea1",
+   "id": "addaa346-7a88-4c18-9f1e-295665959a9d",
    "metadata": {},
    "outputs": [],
-   "source": []
+   "source": [
+    "println(\"Hello, World!\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "3434842c-2af0-4f6a-a70b-a59fb8fcc4af",
+   "metadata": {},
+   "source": [
+    "The name of the function is println. The expression in parentheses is called the argument of the function.\n",
+    "It is common to say that a function “takes” an argument and “returns” a result. The result is also called the return value."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f63d270a-7149-4ffd-bc31-f746560a37ac",
+   "metadata": {},
+   "source": [
+    "Julia provides functions that convert values from one type to another. The parse function takes a string and converts it to any number type, if it can, or complains otherwise:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "1f05465a-4863-4205-9c73-26f0e93f049b",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "parse(Int64, \"32\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "e6ac9994-9cbb-4004-889d-a657b8396063",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "parse(Int64, \"Hello\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "793c9620-7b6e-443c-8765-8136fbfcb071",
+   "metadata": {},
+   "source": [
+    "Julia provides several mathematical functions.\n",
+    "  - abs(x): Absolute value of x.\n",
+    "  - sqrt(x): Square root of x.\n",
+    "  - cbrt(x): Cube root of x.\n",
+    "  - exp(x): Exponential function e^x.\n",
+    "  - log(x): Natural logarithm of x.\n",
+    "  - log10(x): Base 10 logarithm of x.\n",
+    "  - log2(x): Base 2 logarithm of x.\n",
+    "  - sin(x): Sine of x (in radians).\n",
+    "  - cos(x): Cosine of x (in radians).\n",
+    "  - tan(x): Tangent of x (in radians).\n",
+    "  - asin(x): Arcsine of x (result in radians).\n",
+    "  - acos(x): Arccosine of x (result in radians).\n",
+    "  - atan(x): Arctangent of x (result in radians).\n",
+    "  - sinh(x): Hyperbolic sine of x.\n",
+    "  - cosh(x): Hyperbolic cosine of x.\n",
+    "  - tanh(x): Hyperbolic tangent of x.\n",
+    "  - asinh(x): Inverse hyperbolic sine of x.\n",
+    "  - acosh(x): Inverse hyperbolic cosine of x.\n",
+    "  - atanh(x): Inverse hyperbolic tangent of x.\n",
+    "  - floor(x): Largest integer not greater than x.\n",
+    "  - ceil(x): Smallest integer not less than x.\n",
+    "  - round(x): Nearest integer to x.\n",
+    "  - trunc(x): Integer part of x."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d048851b-8eac-4dc3-81b7-ea1d625a1db2",
+   "metadata": {},
+   "source": [
+    "So far, we have only been using the functions that come with Julia, but it is also possible to add new functions. A function definition specifies the name of a new function and the sequence of statements that run when the function is called. Here is an example:"
+   ]
   },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "4ff56e28-969e-4a2d-b33c-21b4a4ecc4de",
+   "id": "fd2f4828-47f5-4df4-b5bd-a42625487b5a",
    "metadata": {},
    "outputs": [],
    "source": []
diff --git a/README.md b/README.md
index 59ab6303bad1bbd0f95d1a130d60808434eff71d..4415f6880c5d1f7fecdfb5f0db17b8e6e34a2a0c 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 Material for the Julia seminar course.
 The course material is adapted from two sources:
   - the [course](https://github.com/mfherbst/2022-rwth-julia-workshop.git) from Michael Herbst ([MIT license](https://opensource.org/license/mit/)).
-  - the book [ThinkJulia](https://benlauwens.github.io/ThinkJulia.jl/latest/book.html) from Ben Lauwens ([Creative Commons Attribution-NonCommercial 3.0 Unported license](https://creativecommons.org/licenses/by-nc/3.0/deed.en)).
+  - the book [ThinkJulia](https://benlauwens.github.io/ThinkJulia.jl/latest/book.html) from Allen Downey and Ben Lauwens ([Creative Commons Attribution-NonCommercial 3.0 Unported license](https://creativecommons.org/licenses/by-nc/3.0/deed.en)).
 
 ## Software and material
 What you need for the workshop (quick overview):