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	-  (en)
 
	- Same data, normalized to 1997 values to show relative change in lanes, centers and membership (en)
 
	- PBA bowler John Furey uses a conventional  delivery. Finger rotation can induce axis rotation, causing the ball to hook . (en)
 
	- The average number of lanes per bowling center has trended upward slightly during this time period. (en)
 
	- Traditional scoring of a spare:
Frame one:  + 4 = 14
Frame two: 4 + 2 = 6 → Total = 20 (en)
 
	- 17.5 (dbd:second)
 
	- An 1838 Indiana newspaper describes how tenpin bowling was devised to evade a Baltimore statute prohibiting nine-pin bowling. (en)
 
	- An 1839 liquor license ordinance prohibited gambling in "any ball, nine or ten pin alley"—associating bowling with gambling and  games having a "demoralizing tendency". (en)
 
	- In about 2015, U.S. bowling center employment reversed a long decline, which some attribute to their diversification into more broad-based entertainment centers. (en)
 
	- Delivery styles often involve a long follow-through and widely extended balance arm and leg. (en)
 
	- Top view: Ideal impact for strike (en)
 
	- An early  newspaper ad features a "Ball and Ten Pin Alley" to attract customers to a "Baking and Confectionary Business". (en)
 
	- Simplified sport pattern: a "flatter"  distribution of oil across the lane presents a greater challenge to hit the pocket. (en)
 
	- Ball contacts the 1, 3, 5, and 9 pins  to achieve a strike. (en)
 
	- Bowling alley at the Pleasant Beach Hotel, Bainbridge Island, Washington (en)
 
	- Human pinsetters  preceded automated mechanical pinsetters. (en)
 
	- An 1829 newspaper editorial describes those who frequent bowling alleys and taverns: "the young, the frivolous, the headstrong, ... men of coarser passions and appetites, and fond of more riotous pleasures"—reflecting the often negative image bowling had. (en)
 
	- USBC membership has declined, indicating waning league participation in the U.S. Figures do not include members of leagues that are not USBC-certified. (en)
 
	- Traditional scoring of a strike:
Frame one: 10 +  = 19
Frame two: 3 + 6 = 9 → Total = 28 (en)
 
	- Video: The two-handed delivery, widely popularized by Jason Belmonte, increases potential rev rate and hook. (en)
 
	- Front view: the ball impacts center pocket at "board 17.5"—found by a USBC pin-carry study to maximize strike probability. The ideal impact point is closer to the center of the head pin than many believe. (en)
 
	- Two-handed delivery: Both hands retain contact with the ball until just before the release. (en)
 
	- Though it is often incorrectly called a two-handed release, the actual release involves a single dominant hand for most bowlers. (en)
 
	- An 1895 advertisement for bowling lockers  suggests the attire and facilities used by bowlers of the era. (en)
 
	- Simplified THS : relatively dry areas on the sides, and more heavily lubricated areas surrounding the centerline, help to guide the ball toward the pocket. (en)
 
	- For most two-handed deliveries, the thumb is never inserted into the ball in the first place, allowing a high rev rate and resultant hook. (en)
 
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