In fact inspection shows none of these sources has been consulted. They either aren't cited in the first place, or are trivial or spurious, or copied from other articles. We can detail them as follows:
* Barr: This is simply a catalogue of van Gogh paintings, available as a Google book, and one of five offered citations for the holding museum.
* de la Faille: The citation is copied from Farms near Auvers and is used incorrectly to say F750 echoes F793, whereas in fact de la Faille at p. 303 compares F793 with F806 (same location). The cartel missed on what anyone consulting these works would have picked up immediately, that Houses at Auvers F759 is the same location as that in Thatched Cottages in Auvers F780.
* Hulsker: Not cited at all
* Maurer: Available as a Google book and as noted above a spurious citation for Corinne's "the inner spirituality of man and nature" quotation.
* Pickvance: Available as a Metropolitan Museum download . Used merely to cite that the painting has been exhibited all over the world. If the cartel had actually consulted the pages 234- 235 they cite, they would have discovered that the house had previously been painted by Cézanne, that it belonged to a stonemason and that it was the same location as F780 we mention immediately above.
* Van der Veen & Knapp: Cited twice as sources for paintings. The first is copied from Thatched Cottages and Houses and the second from Farms near Auvers. If the cartel had actually consulted van der Veen & Knapp, they would have been better able to present the old chestnut that Vincent sold only a single painting in his life as along the lines noted by C1cada on the Talk page (essentially he sold all his paintings to his art dealer brother Theo in return for a stipend to support himself).
* Walther: Not cited at all.
In reality the cartel's article was sourced entirely from the web. It's quite plain none of their editors had any expertise in van Gogh paintings, or for that matter any significant knowledge of them let alone pleasure in studying them.
Je suis Hafspajen, queen of queens, douche of douches
We turn now to "peasant life and their cottages". In our C1cada page, our editor (Marinka) said this was due to the editor 7&6=thirteen. It's true that this editor brought "peasant life and their cottages" into the lede in preparation for its DYK nomination, but the origin was an edit by Hafspajen shortly after she created the article. We shall look at that in a moment, but it's instructive first to look at 7&6=thirteen's sourcing.
When 7&6=thirteen brought it into the lede, he at first provided a source only for the 77 Auvers paintings assertion. This was David Brook's site. He later provided two sources for "the peasant life and their cottages" assertion. These are [A] and  you see in the snapshot of the lede above and neither were Hafspajen's original source. [A] is a note quoting the holding museum website, but it doesn't support "peasant life and their cottages" (it merely talks about a cluster of dwellings), while  is a magazine article devoted to Vincent's earlier experience as a lay preacher in the coalmining Borinage district of Belgium before he vowed to become an artist. It is true that the article avers that Vincent retained his interest in cottagers to the end at Auvers, but the Borinage cottagers were miners and not peasants and the article doesn't imply that the Auvers cottagers were peasants (in fact they were landed farmers, prosperous and progressive members of the Auvers community, such peasantry as there ever were at Auvers long since emancipated). It's slightly amusing to note, as Marinka did, that "cottaging" is Brit slang for the unconventional use of public toilets by gay men and that 7&6=thirteen began his distinguished career at Wikipedia outing celebrity cottagers.
This is the link to Hafspajen's original edit, the contents of which we snapshot below (they are two separate passages and the second does not run on from the first):