Does Sheikh Al-Albani's book Silsilat al-Ahadith al-Sahihah contain hadiths from the Four Sunan, or other compilations like Imam Ahmad's Musnad?

Shaykh Al-Albani's Silsilah Sahihah (The Authentic Series) contains many hadiths that are outside the Six Books, such as Al-Musnad and Al-Tabarani's Mu'jam collections, among others. The series began with articles published in newspapers and then compiled into volumes. The Shaykh continued to issue new volumes comprising his hadith authentications, categorizing them as authentic (sahih) or weak (da'if).