Explain, in public provisions, the difference between observational and speculative concepts. Then manifest the difference with a or-laws system of your dainty. That is, determine restraint some or-laws system T which speculative concepts are introduced by T. Further, determine the concepts which are used to recount the phenomena that T is reputed to interpret.
Citation style: preferably some author-year-style, such as Chicago.
G. Schurz: Philosophy of Science. A Unified Approach, 2014.
R. Carnap: Philosophical Foundations of Physics, Chapter 23 — 25, 1966.
H. Andreas: Speculative Provisions in Science, Stanford Encyclopedia of Philosophy, http://plato.stanford.edu/entries/theoretical-terms-science/.