2

I'm trying to draw a sequence of arrows with xy-pic that extends over two lines, and so I need to draw an arrow joining the end of the first line with the beginning of the second line. Here's the code I've tried:

\documentclass{amsart}
\usepackage[all]{xy}

\begin{document}

\[
\xymatrix{
\cdots\ar[r] & \mathrm{K}_j(M^{p+1}) \ar[r]^{i^p_j} &\mathrm{K}_j(M^{p}) 
\ar[r]^{q^p_j} & \mathrm{K}_j(M^{p}/M^{p+1}) \ar`r[d] `d[dl] 
`l[ddlll]_{b^p_j} `d[ddll] '[ddll]&\\
& & & &\\
& \mathrm{K}_{j-1}(M^{p+1}) \ar[r]^{i^p_{j-1}} &\mathrm{K}_{j-1}(M^{p}) 
\ar[r]^{q^p_{-1}} & \mathrm{K}_{j-1}(M^{p}/M^{p+1}) \ar[r] & \cdots
}
\]

\end{document}

This produces the following output, which is almost what I want.

Arrow

The problem is that the head of the arrow joining the first and the second line is not positioned correctly. I have a suspicion that this is due to me not understanding the syntax of xy-pic correctly, so I would be glad if someone could point out what I'm doing wrong.

Edit: I just realized that there is a typo in the above code: I typed an apostrophe instead of a backquote in front of the last target of the relevant arrow. The code should read

\documentclass{amsart}
\usepackage[all]{xy}

\begin{document}

\[
\xymatrix{
\cdots\ar[r] & \mathrm{K}_j(M^{p+1}) \ar[r]^{i^p_j} &\mathrm{K}_j(M^{p}) 
\ar[r]^{q^p_j} & \mathrm{K}_j(M^{p}/M^{p+1}) \ar`r[d] `d[dl] 
`l[ddlll]_{b^p_j} `d[ddll] `[ddll]&\\
& & & &\\
& \mathrm{K}_{j-1}(M^{p+1}) \ar[r]^{i^p_{j-1}} &\mathrm{K}_{j-1}(M^{p}) 
\ar[r]^{q^p_{-1}} & \mathrm{K}_{j-1}(M^{p}/M^{p+1}) \ar[r] & \cdots
}
\]

\end{document}

which produces the following output.

Arrow2

This outcome is unfortunately even worse.

1
% arara: pdflatex

\documentclass{amsart}
\usepackage[all, cmtip, pdf]{xy}

\begin{document}
\[
\xymatrix{
\cdots\ar[r] & \mathrm{K}_j(M^{p+1}) \ar[r]^{i^p_j} &\mathrm{K}_j(M^{p}) 
\ar[r]^{q^p_j} & \mathrm{K}_j(M^{p}/M^{p+1}) 
\ar`r[d] `d[dl] `l[ddlll]_{b^p_j} `d[ddll] [ddll] & \\
& & & &\\
& \mathrm{K}_{j-1}(M^{p+1}) \ar[r]^{i^p_{j-1}} &\mathrm{K}_{j-1}(M^{p}) 
\ar[r]^{q^p_{-1}} & \mathrm{K}_{j-1}(M^{p}/M^{p+1}) \ar[r] & \cdots
}
\]
\end{document}

enter image description here

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