Al-Madkhal ila Madhhab al-Imam Ahmad ibn Hanbal - Ibn Badran

Very nice edition authenticated and annotated by Abdallah at-Tourki.
Tahqiq: د. عبد الله بن عبد المحسن التركي
Pages: 520
Edition: مؤسسة الرسالة

A magnificent Saudi edition with a new Tahqiq based on the author's manuscript, which corrects Abdallah at-Turki's edition on a number of points. The Muhaqqiq has also taken care to cite references and sources at the bottom of the pages, as well as other useful annotations for the reader.
Tahqiq: سلمان بن حمدان الهزيمي
Pages: 576
Edition: دار طيبة الخضراء