Published in Proceedings of the Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 214-293

Published in Proceedings of the Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 14-82

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 83

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 360-382

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 136-188

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 331-336

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 294-295

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 209-213

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 296-328

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 120-135

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 203-206

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 84-111

Published in Proceedings of The Academy of Natural Sciences of Philadelphia, in 1920, in volume 72, pages 385-402