..............................................................................................................................................1 ..........................................................................................................1..........................................................................................................4............................................................................................15............................................................................................................19 ............................................................................................................................................23 ........................................................................................................................34 ...............................................................................................................34...............................................................................................................34...............................................................................................................35 ........................................................................................................................39 .......................................................................................................39 ...............................................................................................50 ...................................................................................................53...................................................................................................55.......................................................................................57...............................................................................................................60...............................................................................................60...............................................................................................61...............................................................................................63...............................................................................................69...............................................................................................71.......................................................................................................73...............................................................................................................74........................................................................................................................................79 − − − − −−− −−− −−−−−−−− −₂ −₂ ₂ − − − − − − − −− ₂ ₂ ₂ 84