Reproducing image of text boxes in a cycle using TikZ

I'm looking for a way to create a loop of text boxes such as the one below.

I tried creating the image myself, however I couldn't find a way to place the arrow heads ontop of the circle, the circle also were visible inside the text boxes.

This question is similar, but I'm looking for black and white diagrams, and I'm also interested in the arrowheads ontop of the lines.

• Please post the code you tried so people do not have to start from scratch. It will make it a lot easier for people to help if you provide the code to draw the boxes and circle as people can then concentrate just on the specific problems you are experiencing. – cfr Dec 16 '14 at 16:57

You could try something like this:

\documentclass[border=5mm,tikz]{standalone}
\usepackage{mwe}
\usepackage{tikz}
\usetikzlibrary{shapes.misc,arrows,decorations.markings}
\tikzset{->-/.style={decoration={markings,
mark=at position 0.5 with {\arrow{stealth}}},
postaction={decorate}}
}

\begin{document}
\begin{tikzpicture}
\node[rounded rectangle, draw] (A) at (180:2) { \hspace*{20mm} };
\node[rounded rectangle, draw] (B) at (90:1.8) { \hspace*{20mm} };
\node[rounded rectangle, draw] (C) at (0:2) { \hspace*{20mm} };
\node[rounded rectangle, draw] (D) at (270:1.8) { \hspace*{20mm} };
\draw[->-](A) to [bend left] (B.south west);
\draw[->-](B.south east) to [bend left] (C);
\draw[->-](C) to [bend left] (D.north east);
\draw[->-](D.north west) to [bend left] (A);
\end{tikzpicture}
\end{document}


This produces: