Because there is no stated or implied ranking of the six necessary and sufficient conditions and they are only effective in combination, it may be a mistake to favour one above the other
2011 ◽
Vol 84
(2)
◽
pp. 238-254
◽
1973 ◽
Vol 15
(3)
◽
pp. 279-290
◽
1991 ◽
Vol 33
(3)
◽
pp. 275-279
◽
1983 ◽
Vol 27
(2)
◽
pp. 137-150
◽
2013 ◽
Vol 2013
◽
pp. 1-9
◽