His next and final book, The Soundless Sahara, was published in 1968; according to the book's back cover he spent part of his years living in Massachusetts, and the rest in either England or France.
Buku berikutnya dan terakhir, The Soundless Sahara, diterbitkan pada 1968; menurut sampul belakang buku tersebut, ia menjalani sebagian tahun-tahunnya tinggal di Massachusetts, dan sisanya di Inggris atau Prancis.