Regular and singular perturbations

L '

8 9 : < '

89 A

A

FG B "

89

A

FG Q

FG B "

Q "

89

A

<

7 < "

89< "

89 7 <

8 9 8 # $9 )

% < % #

'

< 2

FG "

89

< 2

+ 8 9<

S 8

< 2

'

< 2

< % )

389< N B 89< 3 )

89< 2

89

: A

+

89

89 $ $ )

89 89 7<

% 8

89

899 89 B

89 Q Q

89<

89 89 B 89 !