documentclass{article}
usepackage[utf8]{inputenc}
usepackage[T1]{fontenc}
usepackage[full]{textcomp}

usepackage{tikz}
usetikzlibrary{calc}
usetikzlibrary{cd,positioning,shapes}
usetikzlibrary{decorations.pathmorphing}
usetikzlibrary{decorations.markings}

begin{document}
Let $Delta$ be a connected Dynkin diagram, and
let $Delta^+$ be the extended (or affine)
Dynkin diagram associated with~$Delta$.
Then $Delta^+ = Delta sqcup {alpha_0}$.
Below we depict the connected extended Dynkin diagrams,
in which $alpha_0$ is depicted by a grey node
tikz node[draw,circle,inner sep=2pt,fill=gray] {};.
 [
 begin{tikzpicture}[
  yscale=-1.3,
  every node/.style={draw,circle,inner sep=2pt},
  every label/.append style={rectangle,font=footnotesize,
   inner sep=1ex,text depth=1pt},
  decoration={markings},
  doubledynkin/.style={double distance=2pt,postaction=decorate},
  a0/.style={fill=gray}
  ]
  node[draw=none] (A1text) [label=right:{normalsize$A_1^+$:}] at (-.5,0) {};
  node[a0] (A10) at (1,0) {};
  node (A11) at (2,0) {};
  draw[double distance=2pt,
  decoration={
  mark=at position 0.95 with {arrow{>}},
  mark=at position 0.36 with {arrow{<}}
  },
  postaction=decorate] (A10) -- (A11);

  begin{scope}[xshift=5cm]
   node[draw=none] (Antext) [label=right:{normalsize$A_n^+$ ($n ge 2$):}] at (-1.5,0) {};
   node[a0] (An0) at (3,-0.7) {};
   node (An1) at (1,0) {};
   node (An2) at (2,0) {};
   node (Annm1) at (4,0) {};
   node (Ann) at (5,0) {};
   draw (Annm1) -- (Ann) -- (An0) -- (An1) -- (An2);
   draw[dashed] (An2) -- (Annm1);
  end{scope}
 end{tikzpicture}
]
end{document}