\documentclass[10pt]{article}
\usepackage{pgf,tikz}
\usetikzlibrary{arrows}
\pagestyle{empty}
\begin{document}
\begin{tikzpicture}[line cap=round,line join=round,>=triangle 45,x=1.0cm,y=1.0cm]
\clip(1.58,0.82) rectangle (7.08,5.06);
\draw [->] (2.04,2.56) -- (4.12,4.6);
\draw [->] (4.12,4.6) -- (5.56,3.5);
\draw [->] (2.04,2.56) -- (5.56,3.5);
\draw [->] (2.04,2.56) -- (6.52,2.62);
\draw [dash pattern=on 1pt off 1pt] (4.12,4.6)-- (4.14,2.59);
\draw [dash pattern=on 1pt off 1pt] (5.56,3.5)-- (5.58,2.61);
\draw [dotted] (5.58,2.6)-- (5.82,2.6);
\draw [dotted] (5.82,2.6)-- (5.82,2.84);
\draw [dotted] (5.82,2.84)-- (5.58,2.84);
\draw [dotted] (5.58,2.84)-- (5.58,2.6);
\draw [dotted] (4.12,2.58)-- (4.36,2.58);
\draw [dotted] (4.36,2.58)-- (4.36,2.82);
\draw [dotted] (4.36,2.82)-- (4.12,2.82);
\draw [dotted] (4.12,2.82)-- (4.12,2.58);
\draw (2.64,4.3) node[anchor=north west] {$ \mathbf{B} $};
\draw (5.14,4.5) node[anchor=north west] {$ \mathbf{C} $};
\draw (6.6,3.02) node[anchor=north west] {$\mathbf{A}$};
\draw (3,2.64) node[anchor=north west] {$B_A$};
\draw (4.72,2.7) node[anchor=north west] {$C_A$};
\draw [->] (2.06,1.74) -- (5.58,1.74);
\draw [->] (5.58,1.74) -- (2.06,1.74);
\draw (3.46,1.72) node[anchor=north west] {$ (B+C)_A $};
\draw (3.52,3.72) node[anchor=north west] {$ \mathbf{B}+\mathbf{C} $};
\end{tikzpicture}
\end{document}