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            <h2><font color="#ffffff">Search Algorithms: CCD</font></h2>
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<p>The CCD algorithm (due to Thomas Richardson) is operated in the
    same way as the PC algorithm. The output is interpreted subject to the
    same restrictions as the PC algorithm, with the exception that CCD will
    return PAGs that can only be consistently interpreted as cyclic
    graphs.</p>
<p>The algorithm is pointwise consistent for linear systems with Normal
    distributions, no latent variables and no correlated twoCycleErrors. It is
    similarly consistent for categorical variables with a Multinomial
    distribution if the true causal graph and the distribuiton satisfy the
    local Markov conditon--which is quite restrictive for categorical
    variables for cyclic systems.</p>
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