https://daringfireball.net/linked/2007/03/19/itunes-71-sort
Daring Fireball: Sort Fields in iTunes 7.1
daring fireballsort fieldsitunes 71
https://www.chronoengine.com/forums/topics/view/109225/a-method-to-build-differents-filters-on-differents-fields-on-a-view-list-with-paginator-and-sort-columns
A method to build differents filters on differents fields on a view list, with paginator and sort...
How to build multiple filters on different fields in a list view with pagination and sorting.
https://www.drupal.org/node/2202093
Search API Sorts Inability to add new sort fields after upgrading to 1.5 [#2202093] | Drupal.org
Jan 23, 2016 - I just upgraded from 1.4 to 1.5 and added a new index to solr. The ability to add new sort fields went away in 1.5. I then upgraded to the latest dev version...