Coal the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to
Brown Bear, Brown Bear, What Do You See? animals. The book was one of the "Top 100 Picture Books" of all time in a 2012 poll by "School Library Journal". As of 2013, it ranked 21st on a Goodreads list of "Best Children's Books," and the publisher claimed that there were "7 million copies in print in various formats and languages." In 2010, the Texas State Board of Education briefly removed the book from the public school curriculum after confusing the author with philosopher Bill Martin, author of "Ethical Marxism: The Categorical Imperative of Liberation". Brown Bear, Brown Bear, What Do You See? Brown Bear, Brown Bear, What