When any reference or recital is made in any recorded instrument as to any restriction, agreement, easement, mortgage or other encumbrance of any kind affecting real property, customarily created by recorded instrument or instrument of which a notice or statement provided by statute is recorded, or as to any such encumbrance in general terms, and the reference or recital does not specify the public records and place therein where the instrument creating the encumbrance or such notice or statement of it is to be found, the reference or recital shall unless a contrary intent clearly appears be construed to refer only to encumbrances, if any, of the kind therein described created by instruments included, or of which such a notice or statement is included, in the chain of record title to the real property affected within a period of twenty years prior to the recording of the reference or recital, and the fact that there are none within the period shall not be construed to indicate a contrary intent.