0000929966-99-000003 DEF 14A 1 19981231 19990429 TGC INDUSTRIES INC 0000799165 2673 742095844 TX 1231 DEF 14A 34 000-14908 99604906 1304 SUMMIT AVE STE 2 PLANO TX 75074 9728811099 1304 SUMMIT AVE STE 2 PLANO TX 75074 DEF 14A 1 000092996699000003-001-seq1-def-14a.txt