The sufficient condition for an extremum in the classical action integral as an eigenvalue problem
2013 ◽
Vol 444-445
◽
pp. 625-627
1990 ◽
Vol 116
(1-2)
◽
pp. 177-191
1972 ◽
Vol 30
◽
pp. 132-133
2006 ◽
Vol 11
(1)
◽
pp. 13-32
◽
2017 ◽
Vol E100.A
(12)
◽
pp. 2764-2775
◽