Sorting by author name first, then by year

[pietru]

I have a texinfo file with blocks as below, sorted first by year, then by author
surname using strings starting with "bibl-".  The contents of each block are 
embedded
within "@ifset" and "@end ifset".

Now I want to sort them, first according to surname, then by year, the earlier 
year
put first.

So I am looking to make a function that could do it.

--------

@ignore
* bibl-bouee-poli-etal-2013
@end ignore
@ifset show-bouee-poli-etal-2013
@sp 1
@anchor{bibl-bouee-poli-etal-2013}
2013.@: @sc{Bou@'ee, P.}; Poli, P.; Campillo, M.; Pedersen, H.; Briand,
X.; Roux, P.; @strong{Teleseismic correlations of ambient seismic noise
for deep global imaging of the Earth.} Geophysical Journal
International, Volume 194, Issue 2, Pages 844-848.
@uref{https://academic.oup.com/gji/article/194/2/844/2116979,,
[@sc{Complete Article}]} [@code{bibl-bouee-poli-etal-2013}].
@c Published: April 16, 2013.
@end ifset

@ignore
* bibl-verschuur-2013
@end ignore
@ifset show-verschuur-2013
@sp 1
@anchor{bibl-verschuur-2013}
2013.@: @sc{Verschuur, Dirk J.}; @strong{Seismic multiple removal
techniques.}
@uref{https://bookshop.eage.org/product/seismic-multiple-removal-techniques-past-present-and-future-revised-edition/,,
[@sc{Citation Doi}]} [@code{bibl-verschuur-2013}].
@c Published: January 01, 2013.
@end ifset