The Petra Mathers collection includes correspondence to Petra Mathers from various people at her publishers, Aldred A. Knopf. Most of the letters are from Anne Schwartz, her publisher and are signed Anne. Additional letters in the collection are from Ed Miller and Haven Colgate. Two of the letters were attached to two different manuscripts. The majority of the correspondence, however, was given to The Zimmerli in no discernable order other than chronologically. Luckily all of the letters are dated so it is easy to return them to their original order.

In the first letter dated November 15, 1990 Mathers' editor, Anne, writes about her concerns after having read Petra's "wonderful story." It is interesting to note that the main character's name is Elizabeth; she has not yet been renamed Rosa. At this point the editor mentions some of the areas that need to be reworked or considered further. Namely, the editor feels that the character of Elizabeth needs to show more emotion. Schwartz also notes the inconsistencies regarding schooling and the lack of male characters. She also feels that the story needs more dialogue. Lastly, the editor admonished Petra not to "start the art!" as they need to "get the text working and the project under contract" first.

By the second letter from Anne dated April 1, 1991 the story is being referred to as "the Blackforest story." This letter was attached to the third manuscript draft which helps to establish an approximated date for the manuscript. The handwritten notes on the manuscript show the transition of the main characters name from Elizabeth to Rosa.

The fourth manuscript arrived at The Zimmerli with a letter to Petra from Anne dated October 17, 1991. By the time this letter was written the transition to the name Rosa is complete. In this letter, Anne continues to impress upon Petra to add more dialogue because it "is needed to keep us engaged." Anne and Petra are engaged in an ongoing debate over whether or not to include any references to Rosa's father. This is also reflected in the artwork found in the dummy book. The drawing of the Champaign factory where Rosa's father worked predates the decision to leave him out of the story completely in order to concentrate on Rosa's relationship with her mother. Lastly, Anne asks that Petra to consider writing a short introduction. Ultimately this introduction begins "Dear Readers."

From the dummy book	From the dummy book

There is a gap of almost a year between this letter and the next, which is dated October 1, 1992. Once again Anne expresses how much she loves the revisions. In this letter, Anne addresses the overall flow of the text and indicates the places she would like to see additional dialog. Again Anne extols Petra to write an introductory author's note to "explain the autobiographical elements of the story - and also place it in some kind of historical context."

Anne's next letter dated October 19, 1992 comes less than three weeks after her last letter. Petra's revisions must have been completed in record time. Anne praises the revisions as being "just wonderful" and once again she has to press Petra to write an introduction.

Again, Petra responds quickly because Anne's next letter is dated November 6, 1992. The letter is entirely devoted to issues surrounding Petra's long awaited introduction. Anne is trying to understand Petra's reasoning behind her writing the introduction in the third person because she sees a strong need for Petra to write in the first person. Compare the different versions of the introduction included in the Zimmerli collection.
The discarded Introduction
The Introduction from the Photomechanical
The Introduction in the published book

Next in the line of correspondence comes a letter dated January 18, 1993 from Ed Miller. This letter discusses details about the layout of the book, now referred to as "Kisses for Rosa." This represents a change from Rosa in the Blackforest as the book was named in Anne's last letter dates some two months earlier.

The next to last letter in the correspondence series comes from Ed Miller dated some six months later on October 26, 1994. The layouts are almost finalized. Ed points out some concerns. In particular, he would like some additional artwork of the mailman to include on page 26. This illustrates the not uncommon phenomena of last minute changes made to a book.

The last letter in the series is from Haven Colgate, an editorial assistant who writes Petra on April 24, 1996 that the Child Study Committee at Bank Street College (NY) included Kisses from Rosa in it's annual annotated bibliography of Children's Books.