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[msh-tlba]

Read these plz :
it says : pascal's symbol is ' Pa '

http://www.wikipedia.org/wiki/Pascal_(unit)

http://www.wikipedia.org/wiki/Pressure

http://www.wikipedia.org/wiki/Atmosphere_(unit)

dont forget that in st's book , p.397

Pa , isnt written like that ( Pa ) ... It is written with special physical form which makes the letter (a) under letter ( P)