Nobles were born into a noble family, adopted by a noble family (this was abolished in 1633) or ennobled by a king or Sejm for various reasons (bravery in combat, service to the state, etc.—yet this was the rarest means of gaining noble status). Many nobles were, in actuality, really usurpers, being commoners, who moved into another part of the country and falsely pretended to noble status. Hundreds of such false nobles were denounced by Hieronim Nekanda Trepka in his Liber generationis plebeanorium (or Liber chamorum) in the first half of the 16th century. The law forbade non-nobles from owning nobility-estates and promised the estate to the denouncer. Trepka was an impoverished nobleman who lived a townsman life and collected hundreds of such stories hoping to take over any of such estates. It does not seem he ever succeeded in proving one at the court. Many sejms issued decrees over the centuries in an attempt to resolve this issue, but with little success. It is unknown what percentage of the Polish nobility came from the 'lower' orders of society, but most historians agree that nobles of such base origins formed a 'significant' element of the szlachta.
What did the nobles lose by being denounced?
owning nobility-estates and promised the estate to the denouncer

During the 19th century, Karl Marx and Friedrich Engels extended the concept of materialism to elaborate a materialist conception of history centered on the roughly empirical world of human activity (practice, including labor) and the institutions created, reproduced, or destroyed by that activity (see materialist conception of history). Later Marxists developed the notion of dialectical materialism which characterized later Marxist philosophy and method.
What type of materialism defined the Marxist philosophy?
dialectical materialism

The Greek islands are traditionally grouped into the following clusters: The Argo-Saronic Islands in the Saronic gulf near Athens, the Cyclades, a large but dense collection occupying the central part of the Aegean Sea, the North Aegean islands, a loose grouping off the west coast of Turkey, the Dodecanese, another loose collection in the southeast between Crete and Turkey, the Sporades, a small tight group off the coast of northeast Euboea, and the Ionian Islands, located to the west of the mainland in the Ionian Sea.
The Sporades islands are located where?
off the coast of northeast Euboea