dont split PTEP articleIDs at letter in the middle

[fschwenn]

at the moment
"[1] Iso S. and Orikasa Y. Prog. Theor. Exp. Phys. 2013, 023B08 (2013)."
is split into
"999C5 $$o1$$hIso S. and Orikasa Y.$$sPTEP,2013,023$$m08$$y2013"
but it should be
"999C5 $$o1$$hIso S. and Orikasa Y.$$sPTEP,2013,023B08$$y2013"