COHERENCE NARROWING AND SHIFT OF OPTICAL DOUBLE RESONANCE SIGNALS IN THE (4 s 4p) 1P1 STATE OF Ca AT HIGH MAGNETIC FIELD G. HUBER et E.-W. OTTEN J. Phys. Colloques, 30 C1 (1969) C1-28-C1-30 DOI: 10.1051/jphyscol:1969107