X-28. PETTERSSON, HANS, and KULLENBERG, BORGE. A vacuum 

 core- sampler for deep-sea sediments, Nature , vol. 145, p. 306, 

 1940. 



X-29. PHLEGER, F. B, and PARKER, F. L. Ecology of Foraminifera, 

 northwest Gulf of Mexico. New York: Geological Society of 

 America, Memoir 46. Various pagings. 1951. 



X-30. PIGGOT, C. S. Factors involved in submarine core sampling, 

 Bulletin of the Geolo g ical Society of America , vol. 52, p. 1513- 

 1524, 1941. 



X-31. RICHARDS, A. F. Engineering properties of epicontinental 

 sediments, p. 656-657. In: International Oceanographic Con- 

 gress, 31 August - 12 September, 1959, preprints of abstracts 

 of papers. Washington: American Association for the Advance- 

 ment of Science. 1022 p. 1959. 



X-32. SILVERMAN, MAXWELL. The possibility of contamination in 

 underwater piston core samples. M. S. Thesis, Illinois University. 

 Unpublished. 60 p. 1956. 



X-33. SMITH, W. O. Recent underwater surveys using low-frequency 

 sound to locate shallow bedrock, Bulletin of the Geolo g ical 

 Societ y of America , vol. 69, p. 69-97, 1958. 



X-34. U. S. HYDROGRAPHIC OFFICE. Instruction manual for oceano- 

 graphic observations. Hydrographic Office Publication No. 607. 

 2d ed. Washington: U. S. Govt. Print. Off. 1 vol. (loose-leaf), 

 p. 1-210, 1955. 



X-35. WEIBULL, WALODDI. The thickness of ocean sediments meas- 

 ured by a reflection method. [No.] 12, p. 1-17. Jnj Meddelanden 

 fran Oceanografiska Institutet, ^Nosfl 11-20. Goteborg. Various 

 pagings. 1946-1952. 



X-36. WORZEL, J. L. Extensive deep-sea sub-bottom reflections 

 identified as white ash, National Academ y of Science Proceed- 

 ings, vol. 45, no. 3, p. 349-355, March 1959. 



X-37. WRATH, W. F. Contamination and compaction in core sampling, 

 Science , n.s., vol. 84, p. 537-538, 1936. 



X-38. ZENKOVICH, V. P. Sea bed. [Translated from the Russian by 

 I. Lasker] Moscow: Foreign Languages Publishing House. 60 p. 

 1958. 



X-9 



