The Ambrogio Lorenzetti reference article from the English Wikipedia on 24-Apr-2004
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Ambrogio Lorenzetti

Time you got around to sponsoring a child
Ambrogio Lorenzetti (or Ambruogio Laurati) (c. 1290 - 1348) was a Sienese painter, he was born and died in Siena. He was active between approximately 1317 and 1348. His brother was the painter Pietro Lorenzetti. His work shows the influence of Simone Martini, although it is more naturalistic.

Ambrogio's works include

We find the first evidence of the existence of the hourglass on one of his paintings (see external link above). He is believed to have died of bubonic plague circa 1348/9.

Giorgio Vasari includes a biography of Lorenzetti in his Lives.

image: Lorenzetti_gov.jpg
Good Government (left), Bad Government (right)
Circa. 1328