I'm describing parameter search using a particle filter, for which I use West M. (1993) Approximating Posterior Distributions by Mixture.
On page 8 of the document, he states "and $p(\theta)$ is (approximately) a mixture of multivariate normal distributions,
$p(\theta)=\sum_{j=1}^{n} w_j N_p(\theta \mid m_j, M_j)$."
where $N_p(\mu, \Sigma)$ is a p-variate gaussian distribution.
I.e. he's using a conditional probability inside a Gaussian PDF. Is that notation allowed? I've not seen that anywhere. My professor (i'm a PhD student) says it's incorrect.