He is working his servants hard.

Don't be afraid to kick it around a little. It is sturdy.

The earliest use of latent variable ideas in time series appears to have been due to Wiggins (1973) but, as so often happens, it was not followed up. […] The basis for this remark can be explained by reference to a simple example which, at first sight, appears to have little to do with latent variables.

a lofty goal