Theorem is non-trivial statement, usually referring to mathematics, that is proved baser on certain set of axioms.
Sometimes the term theorem is used when some statement is formulated, revised as a scientific concept, but the formal proof is still expected to be constructed in near future. For example, the existence and uniqueness of the holomorphic tetration with certain properties is declared as theorem in the first publication  on it, while the proof  lated. However, in such cases, the term conjecture may be more suitable.
- http://www.ams.org/mcom/2009-78-267/S0025-5718-09-02188-7/home.html http://www.ils.uec.ac.jp/~dima/PAPERS/2009analuxpRepri.pdf D.Kouznetsov. Analytic solution of F(z+1)=exp(F(z)) in complex z-plane. Mathematics of Computation, v.78 (2009), 1647-1670.
- http://www.springerlink.com/content/u7327836m2850246/ http://tori.ils.uec.ac.jp/PAPERS/2011uniabel.pdf H.Trappmann, D.Kouznetsov. Uniqueness of Analytic Abel Functions in Absence of a Real Fixed Point. Aequationes Mathematicae, v.81, p.65-76 (2011)
- http://physikpraktika.uni-oldenburg.de/download/GPR/pdf/E_Traegheitsmomente.pdf Carl von Ossietzky Universität Oldenburg – Faculty V - Institute of Physics Module Introductory laboratory course physics – Part I. Moment of inertia - Steiner's theorem