You quickly dismiss the other source (France, 1991). Unfortunately this is real science and it costs money, hence only the abstract is freely available.
I asked a kind uni friend to provide me with the paper so let me offer some quotes (I am typing this out so I?ll keep it brief):
?Despite negative opinions and concern there have been few empirical investigations of the effects on infants of using extinction with ISD [Infant Sleep Disturbance]. No studies to date have reported negative side effects of treatment.?
?Although extinction can be modified to make it more palatable to parents, with the exception of Scheduled Awakening no viable alternative to the use of extinction have been developed.?
?Some form of extinction, therefore, is usually the only alternative for parents wishing to change their infant?s sleep behaviour.?
?The subjects for the experimental group were 35 infants (6-24 months) who were treated with an extinction program for their sleep disturbance, either on its own (n = 13) or in conjunction with sedative medication (n = 10) or placebo (n =12).?
?Measures: The Flint Infant Security Scale. This scale measures security in infants up to 2 years of age. Its reliability and validity has been established with adopted infants who moved between homes and families. It was modified to be filled out by parents rather than administered as an interview.?
?Measures: Child Behavior Characteristics Scale. This scale, which was completed by the subjects parents, reliably measures a variety of child characteristics which have been shown to have stability over time. Its validity has been established in a variety of ways (Fanshel, 1975; Fanshe & Shinn, 1975).?
?Using an extinction-based behavior management approach with sleep-disturbed infants did not lead to any deterioration in infant security nor in a variety of the infants? behavior characteristics. On the contrary, there were lasting improvements in the infants? security, likeability, and emotionality/tension. The experimental group [who didn?t sleep well] were significantly less agreeable than the pooled controls [good sleepers] at baseline but this difference had disappeared after intervention [i.e. CC]. All of these improvements are in addition to improvements in sleep behaviour.?
Again, if you don?t trust parents you will probably want to dismiss this study, too.