Complex sentence: He also has served as an advisory editor on several journals concerned with hospice, palliative care, and bereavement, and has edited books on the nature of human attachments, "The Place of Attachment in Human Behaviour" and "Attachment Across the Life Cycle".
Split into simpler sentences: He also has served as an advisory editor on several journals concerned with hospice, palliative care, and bereavement. Parkes has also edited books on the nature of human attachments, "The Place of Attachment in Human Behaviour" and "Attachment Across the Life Cycle".