SBK: Schweizerischer Briefmarkenkatalog, stamp catalogue issued by the Swiss stamp dealers association with own numeration
LBK = Liechtenischer Briefmarkenkatalog, catalog issued by the Liechteinian Post and the Swiss stamp dealer association
Mi = Michel catalog for most countries
SG = Stanley Gibbons for Great Britain and British commonwealth stamps
Fi = Fischer (polish catalogue)
YT =Yvert & Tellier