M. D. Mesarovic has written:

'Theory of hierarchical, multilevel, systems'

'General systems theory'

M. Christine Wilson has written:

'On certain information-theoretic concepts in the theory of graphs' -- subject(s): Graph theory, Uncertainty (Information theory)

Depends what you mean by "respectably."

M Theory, a type of string theory, requires the existence of eleven dimensions in which the strings can vibrate. If you consider M Theory to be "respectable," then the answer is eleven.

If your view of M Theory is that, "It's so bad a theory that it's not even wrong," then you might say that eleven dimensions is not respectable.

It is generally agreed that the M stands for "membrane" though the words magic, matrix, mother, and some others, have been suggested. The scientist who named this theory actually didn't say what the "M" stands for.

M. M. Khapaev has written:

'Averaging in stability theory' -- subject(s): Stability